The overhead of duplicated data across the network. Not reposts on different instances, but the software itself on those different instances needing to cache/store this one single post for their users locally

Lack of centralized control.

Until there's some kind of organizing central committee of servers that could mutually defederate problematic instances, every server is forced to play whack-a-mole to deal with fascists and pedophiles and the like. Every server can not be an island onto themselves, they should be in communication with each other and then collectively decide on the rules of the federation.

Scalability. Most federated Lemmy instances are hobbiest run projects started by every day joes and privacy advocating sysadmins. These instances can handle a modest amount of activity. Lemmy.world is slowing to a crawl and barely working due to being overloaded. At the scale of tens of thousands of active users you NEED proper infrastructure and a dedicated team. These are not things that come easy when the instance generates no revenue besides meager donations. Lemmy.world is looking for on call system operators willing to contribute 5-10 hours per week. Good help is rarely cheap let alone free.

Democracy. All people want it, but many people struggle with it. The comments up in this thread are all basically talking about this topic: People have to agree on what their society should be about. And that ~~can~~ is hard work. It means reconcile and debating. It is not very different from every other Federation like the EU or Germany with its 16 states. Here is an Example:

During COVID, Germany - as a Federation of 16 states - all had to decide on what is the best way to recognize the threat, mitigate it, and build up protections. In the Federal Republic of Germany, that meant that the Goverment took over some aspects, but many things were left to the states (Instances). People had a hard time seeing how this is a good thing. Many people - esspecially conservatives - ask for a strong man and are not able to hold long discussions. They want pragmatic decisions even if it will not guarantee the best outcome in the long run.

The good thing about a Federation is/was, that you have 16 "Working groups" running to the same goal, trying to find their best solutions. Some come up with great ideas on their own, some get inspired how the neighbors do it, some take an international approach and look into europe and some are just overwhelmed with the given task and struggle. People were really put off how "Everyone does his own soup" and some were really angry why there was no central plattform. Like China. Where one man said what to do. Not realizing that this could mean, that this one person has either the right solution, or is ending up locking down whole cities and incarcerating people into camps. For Years. People thing highly of centralized approaches, but do not see how bad it can go - and Germany went to that in a very bad example not only 80 years ago. Yet, we still struggle to see the benefit in Federation as soon as problems arise. In normal times they love Federation.

So my point would be: Federation is great, but the huge downside will be, that we have to talk a lot. Maybe even include a voting tool. Make it secure enough that it can not be abused too much (because it will the bigger the instance gets). We have to define or at least trust certain people, that they will take care of our instances, that we can get behind. And if not, - contrary to living in a Federated country - we are at least able to move to the next instance without a pain (if the instances support account moving one day). But people will get tired of talking too much. They want action. They want a simple and easy solution and continue their life. Some will invest a lot of time into making the instance bearable for many, while some users will just sit in a soft crib, not contributing anything and not understanding why those people "in the glas palast" will not come up with the right solutions. Because they are not debaters. They want pragmatism and will accept more authoritarian instances, if it can make them feel like they are getting lead in a strong way - disregarding if it will play nice with others or not.

In the end, Federated Systems will be a mirror of our societies, closer than what plattforms were ever be able to reflect. But this will come with the exact same problems. I can see a bright future for federated systems if enough people invest their time in it to design the experience what was previously done by worker in multi billion dollar corporations. Now people are given the tools to create their own federated experiences in a digital place. Die instances will prosper by it. Some instances will lose. Some software will burn. Some instances will be too small to have a solid team to answer all this. Some users will be appalled by all of this. But if a critical mass of people can survive and is willing to carry the stick and some form of general consent can be reached via a declaration and a living and growing and changing body of rules, that will adapt to the new challenges of time, it will be THE BEST system out there.

Except if you think a communistic/chinese approach with a central figure and a central single party is the best, that will tell you what the right thing is to do and if you do not follow, your are an deviationist and must be handled/expelled. Some people people love that shit. interestingly, mostly only if they were born into this and were indoctrinated into such a system. There is not a single country in the last 50 years where the people where asked and they willingly decided for themself, that they want such a system. Those systems were always created above the heads of the people - as it is their nature of those systems.

A good approach would be several Cartas that can be nested/cascaded that define what people share as a general consent. Two Instances agreeing into a strong bond of the same value. Another one that wants to join them. Some instances might group as The United Instances of the Fediverse with some basic rights that are not debatable and some views that might change over time. Some communities maybe want to be a left alone and do their own thing with a unorthodox decision tree. Some will not share this carta, so they will come up with their own what would lead to interesting paradoxes or even expose some fallacies in some communities.

Time will show how much strength and endurance we have and how worth it will be for us, to govern our self: Put some things in the hands of the Software we want to use (Government), keep some rules to us (instances) and decide for our own where we want to live as a user. In reality - at least in Germany - it took decades to grow organically. Police and Schools is in the hand of the state, for them to decide what to teach (to some degree) and and when to neglect a criminal/unwanted behavior (to some degree) e.g. for what amount of canabis/hatespeech he can be picked up. In the same way will the instances in the Fediverse define for themself where to draw the line and people will move to those places that give them the best balance of having enough freedoms to life a fulfilling life, but not too much freedom that it will end in anarchy. Basically Democracy.

TLDR:

Pro: Democracy

Contra: Democracy.

One downside/senario I'm worried about is what happens when something really bad happens. Like illegal authorities-get-involved bad? Like leaking sensitive government information or a homegrown r/ jailbait situation that the media catches wind of. Stuff can't be permanently deleted, at least not without nuking everything around it...which people might be tempted to do. And that's basically turning anything seriously incriminating into essentially an infohazard that could get you nuked because you're in an instance where someone else from it commented on the thing or something. And any attempt to and defederation from the offending parties probably isn't the hard shutoff that the authorities would be demanding in such a situation. Even if nothing effectively happens to the greater Federation, it would be a PR nightmare that would probably kill any future attempts of evangelising the platform in the future, especially to bigger communities looking for a new place to stay.

Places like Reddit have mods and admins that worst case scenario, can be the scapegoats. Lemmy doesn't really have that layer of protection because of how esoteric it is to the layman.

You have duplicate communities, posts, etc.

It's hard to find communities.

Evangelizing.

If I want to share a cool link with someone who has an account but is not yet active, I have to:

1. ascertain their instance if they are on the site
2. visit their instance on a browser
3. search their instance for the post I want to share

On centralized platforms I can hit the "share" button the moment I find something interesting. When I do, I will receive a single link that will work for all users of the service.

Granted (because the platform then harasses the user who follows the link, trying to annoy them into getting an account and/or logging in so that it can more accurately harvest their data) it's not a ton better centralized.

But it does make it extra difficult to evangelize this way. I convinced a friend to get an account, and yet when I shared a link with him (without taking the above steps), he sent back a screenshot of the banner telling him he wasn't logged in.

I'd like an easier way to pull the uninitiated into a conversation occurring on this network of sites.

There's much less control about the software.

In a federated system you have no control about wheter remote instances are running up-to-date software or even the same type of software (think Lemmy vs Kbin), which makes breaking changes really hard to impossible, since you never know what ancient version another instance might run.

This is part of the reason why e-Mail works the same now as it did in the 80s. If e-Mail was a centralized service, it would be a full communications- and office-suite now, but since it's federated it's still separate messages in folders and stuff like grouping messages by thread are considered innovative.

Instances being defederated over things like petty drama. Unless it's one that's actively allowing nasty content or people, I don't think that should be the first course of action like some admins seem to treat it as.

From running multiple accounts across multiple instances, I've found that each instance feels like a separate forum of posts. Sure some of the big ones federate with each other, but that still doesn't lead to being able to see the same federated content when you log into infosec.pub or lemmy.world. I think a lot of the differences in content lie with which instances federate with which other instances.

1: Anything that's federated is public (to instance admins) and can't be reliably deleted.

For ActivityPub, that's pretty much everything except user account.

For email (SMTP) that's sender, recipient, subject, and usually body.

Etc. Instance admins can log whatever they want. Laws like the GDPR or CCPA don't apply to all instances.

2: User signup is much harder because choice paralysis over which instance to join often sets in. That in turn leads to default recommendations, resulting in centralization in a few instances. E.g. lemmy.world, beehaw.org, sh.itjust.works, lemmy.ml for lemmy, Gmail, Apple mail, MS Live email, AWS email options for email.

More of a wish than a challenge but federated identities would be awesome. Home instance offline? No problem, just switch servers. No need to try and sync settings and subscriptions between accounts.

Blockchains already do this with public key cryptography. Your "login and password" would just be a Mnemonic Phrase. The fediverse just distributes the public information to use that phrase.

It is difficult to control users, to ban them permanently etc. It is difficult to make money with federated software. You could maybe show ads. But nothing that'd make you rich.

Identity theft. Not as serious as the real life version but imagine that I make an account with your username on another instance, maybe under a domain that's very similar to yours, and start stirring up trouble. If you're someone people recognize I could hurt your reputation or scam people.

Where I notice the most annoying downside to me most is Mastodon: You cannot see any previous discussions and interactions.

When some makes a post I see zero replies, zero boosts, and zero likes when viewing it from another instance. The user also has zero previous posts and zero people following them. When opening the profile on their instance I see hundreds of previous posts, a couple of thousand follows and the toot in question has some likes, some boosts, and a lot of replies.

You have to run and maintain several instances. What if one instance goes down forever?

You cannot censor content. I could make an instance where I post the most vile things and even if 99.99% of lemmy hated my guts and wanted me shutdown I could continue to host my instance and federate with like minded communities. In a non federated platform Admins would delete my instance.

This is a positive to some and a negative to others.

Each individual actor in the system has less incentive to provide value and no incentive to maintain continuity. As a result, you are basically reliant on a small number of unconnected and pseudonymous volunteers who could walk away at any time. Add to that managing a server with thousands of users is basically a part-time job with little pay and you have a system that is sustained by the kindness of a couple dozen strangers.

As we've learned here on hexbear with our recent federation, reddit people are almost unimaginably bad at making memes. Suddenly having your feed look like 9gag is a downside till you block a couple comms

I'll put it this way. In the US, there used to be a rule where, if you broke the law and the police were after you and you drove into another state, the police from the first state you were in had to rely on that state's police to do anything. There was an episode of the Simpsons that spoofed this once. Now apply this to websites.