Once upon a time you could follow someone's public Facebook posts from any RSS reader you liked, whether or not you had an account. Now the only way to follow someone's Facebook posts is to have an account there. And Facebook will probably only show you a small fraction of the posts by the people you actually follow, sorted by what Meta thinks is most likely to make Meta money.

If you trust Meta to not follow a similar playbook with Threads, you are much more optimistic than I am.

I run a small Mastodon instance, and have preemptively defederated from Threads because I do not want Meta to suck in my posts for free and use them as something to spread apart Meta ad views. I've informed my users of this and so far everyone with a reply has praised this decision. They have made choices.

In fact lately there have been waves of spam from the big open-registration instances. I and a lot of other small instance admins I know have responded by limiting our federation with these instances. This creates a slightly worse experience for our users, in that they're likely to stop seeing media from big-instance accounts they follow. And it creates choice - do they talk to their friends on the big instances and say "hey can I persuade you to move to an instance that isn't a spam gateway?" Does the friend say "yes" and acquire an invitation to a closed-registration instance that's well-federated to their friend network? Eventually we end up with multiple networks all on ActivityPub that have very few connections. And this is fine. Because people can also do things like choose to have multiple accounts on these multiple networks.