I already knew that once you put photos up there, you don't own the copyright any more. They do.
That's actually not correct, though it's a common misconception. It's based on a misunderstanding of the Terms of Service.
if you upload a picture to Facebook, you give them an irrevocable license to store and transmit the picture. You have to; after all, you're asking them to...err, store and transmit. The idea is that you can't upload a picture and then sue them for copyright infringement because they have it on their server.
Giving them a license, however, absolutely does not mean transferring the copyright to them. You still own the copyright; you haven't given it away.
What I didn't know, however, apart from this appalling demonstration to me today that they somehow know about my non-F/book Yahoo accounts, was that when you browse for people - relatives in my case - they offer you complete strangers to "friend" who are on your relative's lists. Complete strangers. Never heard of them.
Most likely, they know about the Yahoo account because they see the Yahoo cookie.
A lot o folks tend to form networked social communities; statistically, if someone you know knows someone else, the odds are better than even that you know that person, too. You can always decline to try to contact friends of friends.
I don't use Facebook (except as a repository for my Twitter feed), though I don't find that behavior especially creepy. There's other Facebook behavior I reserve that term for.
