@simsa0 I think one needs to look at the two issues separately: owning your data, and privacy. When it comes to privacy I don't think posting on GNU social is *in theory* that much different from posting on Facebook. It's all public, so anyone can read it. In practice, Facebook is probably much more monitored than some random GNU social site with 10 users. It's probably easier to get a data dump from Facebook that crawl the entire net for random sites (and GNU social instances). If you want true privacy use something like OTR and GPG, and only talk to people you truly trust not to leak your information.

As for owning your own data, I think there's a fundamental difference. If you are on Facebook you basically have to agree to their terms, there's no other choice. With free software platforms you can pick your hosting instance according to the terms, or set up your own if you don't agree with any of them. (Or join with a few friends to set up one, if you can't do it by yourself). I think that's a fundamental difference.