TL;DR: Bluesky isn’t feasibly federated due to hardware demands of self-hosting the relay—which would require every instance to host the same, synced copy of the entirety of Twitter everywhere—among other things, but is great at providing what its committed corporation calls a centralized “credible exit“: “if Bluesky Social PBC goes out of business or loses users’ trust, other providers can step in to provide an equivalent service using the same dataset and the same protocols”