although this is unlikely to substantially and directly impact us and is a more immediate concern for Mastodon and similar fediverse software, we've signed the Anti-Meta Fedi Pact as a matter of principle. that pact pledges the following:
i am an instance admin/mod on the fediverse. by signing this pact, i hereby agree to block any instances owned by meta should they pop up on the fediverse. project92 is a real and serious threat to the health and longevity of fedi and must be fought back against at every possible opportunity
the maintainer of the site is currently a little busy and seems to manually add signatures so we may not appear on there for several days but here's a quick receipt that we did indeed sign it.
Regardless of how untrustworthy Meta as a company is, it also tends to hold the kinds of "mainstream" social media platforms that I have actively been avoiding for many reasons, including their communities. Beehaw has already defederated from other instances for having open sign-up and a disproportionately large number of users on them who needed moderation actions taken, and I can see a Meta-run instance posing the same kinds of problems.
Plus, like others said, it's not impossible to federate later if it ends up being an overreaction. It's just that Meta and its userbase already exist, so it's possible to make pre-emptive judgement with that knowledge and correct the judgement later, potentially avoiding a flood of unwanted content.