I agree to be careful with this one.
I used to chat with this girl all the time on Yahoo Messenger, talking all kinds of real crazy sexual stuff and trying to work her into an offline meeting.
Anyway she asked if I was on Facebook. I didn't think about it and I gave her the info.
Sure enough, she continued the freaky sex talk right out in the open on my facebook wall. Very embarrassing since a lot of my family and old acquaintances are on there.
I had to let her know to cut that stuff out, and then she got offended, it turned into a whole ordeal where I had to constantly be on the lookout for her crazy posts until i finally had to de-friend her.
Some of these people who aren't your personal friends have nothing invested in you and therefore not much trouble publicly trashing you if things go wrong.