@fediversereport I go further in my speculation. I think the opt-in requirement for Threads federation stands out as a signal of where Meta is going. I can't find the quote, but Mosseri has said that the opt-in requirement is to protect their users' privacy, security, and IP rights and defend against spam and abuse.
I call bullshit. Meta has always been crap (intentionally and unintentionally) at those things, even on their own fully-controlled platforms.