We really shouldn’t take this Meta thing lightly.
They could offer the slickest interface and keep people locked to their friends. That interface can use protocols that make it difficult/impossible for non-Threads instances to play ball (ooh this cool new feature is only available through the Threads app; Oh, mybasement.world.ml.xyz can’t read that content). There are many ways to Embrace, Extend, and Extinguish, we’ve seen Meta do it before (e.g. XMPP), and I’m sure we haven’t even thought of some ways Threads could EEE.
I think defederation from Meta’s instances is probably our only option to protect what we have.
@CrazyDuck of course moving to a proprietary protocol doesn’t mean that federation must die. Indeed we kept federation alive for users for a while by bridging gTalk (legacy, still supporting federation) and Hangouts (proprietary). It was the dream of at least a few (myself included) to open up the Hangouts API and/or build federation on top of it, but it was not prioritized – I take part of the responsibility for that, even if I was just an individual contributor: I could have done it as a 20%.