Pretty much the entire bdsm community everywhere was outed on Facebook because folks carried cellphones to events and Facebook started suggesting friends to one another. Fifteen years ago privacy was sacrosanct and no one shared real life names unless they were very close. Now there is no point to trying to keep your identity secret and it sounds silly to introduce yourself as "Master Darkness" or whatever. I mean it sounded silly then, too, but everyone understood the necessity and it was situationally appropriate.

That is the danger of these large corporations. They aren't looking to serve the broad community - they are looking to exploit our social graph for profit regardless of the destruction in their wake.

I'll answer with a blog post by a dissatisfied sysadmin: https://cfenollosa.com/blog/after-self-hosting-my-email-for-twenty-three-years-i-have-thrown-in-the-towel-the-oligopoly-has-won.html

One issue with emails is that it's actually very difficult to self host email servers now as most of the bigger servers would automatically block unknown servers due to spam