So it seems like the biggest concern about Facebook/Meta creating a Fediverse instance, outside of having an "eternal september" is that the instance might be used to datamine other users on the Fediverse.
As far as I know, they can only datamine public posts or private posts that include users on their instance. And even without their own instance, they can still datamine us by using old-fashion web crawlers or scrapping the APIs.
@LukeAlmighty That's why I said "besides the Eternal September" which is a reference to Usenet in which an influx of college students started joining because so many college campuses got Internet access back in 1993.