I'm also seeing a lot of toots from users lobbying their instances to do the same. Including the instance I chose.
Personally I want to see Threads' content and I'd prefer to do so from within Mastodon. But if Mastodon wants to be a nice cozy closed echo chamber instead of federating with those (soon to be) 500M new users that's also fine. It's just not what I was promised/thought I was signing up for, so I'll leave (I won't self host).
Just change to a homeserver that moderates the way you agree with. Mine made a poll and it doesn't look like there will be any restrictions on federating with Threads.
Most celebrities didn't need to be paid to get an email address.
Having corporations participate to fediverse will only be a bad thing, apart from some short term gains.
That said, I'm worried that Meta will only choose to federate with a whitelist of ActivityPub instances, which would certainly be a long term harm to the Fediverse. Maybe they'll prove me wrong though. Zuck is more philosophical than people give him credit for, and I think he's aware of the mistakes he made that caused people to lose trust in Meta. He has an opportunity to embrace (for better or worse) federation as a way to distinguish Meta from its increasingly centralized peers.
It's also an opportunity to expose the disingenuity of Musk, who ironically promised to "turn the platform into 'something new that’s decentralized" [0] but is now suing Meta for making a product that more closely resembles that description than does Musk's recent behavior of view limits and auth walls.
[0] https://www.wired.com/story/twitter-had-a-plan-to-fix-social...
it's possible that it just doesn't matter at all, and in fact the centralization is a selling point for pretty much everyone who isn't a nerd about federation.
we'll see.