Of course it doesn't mean that, but even if it did, what user data are you talking about? The only non-public info that Stack Overflow has from (some) users is their email address and real name, which Facebook already knows.

But facebook can't associate Real Names with questions asked on stackoverflow.

If they had data-sharing in place, they could.

Oh my god, Facebook will know that you asked a question on how to write Hello World in lisp!