Before everyone freaks out, this has zero impact on our communities. Chill.
They can already do this by bringing content from Mastodon to Meta platforms via links and screen grabs, this only speeds up the process.
Personally, I love that they're not federating day one. Because I don't want any instances I use to federate with them, I don't want to be connected to a Meta platform unless I deliberately go to a Meta platform to use it.
To expedite the process, Mastodon instances should just defederate from them entirely. Don't let them access that data through ActivityPub. They can build their own platform on the Fediverse and we can have our network of smaller connected instances.
Them doing this does not affect our communities unless we let it. Defederate from them and we can go on our merry way and they can have their own ad laden instance that's not connected.
Everyone, relax. Continue building your communities here and ignore Meta in their unconnected instances.