Two days ago I heard a story that kept me up all night. A friend's of mine daughter opened her Facebook account, at the whooping age of 7, and added her classmates and family there. So far so good. It has vastly improved her reading skills and her parents were very pleased she uses the internet for something bit more advanced than "create your online Barbi" apps. After a few days in, she received a message from an adult whom she doesn't know who started interrogating her and trying to acquire some details off of her (these were not disturbing questions in the sexual sense of the word, but still - make you suspect what this 30 year old adult has to do with her).
Her dad called me, the online wise and I referred him to Online reverse trace.info - where you can find someone's details and phone # with a simple search (it involved a few dollars to register there, nothing too expensive when it comes to your daughter's protection anyhow). He found the person, who was foolishly using his real name, and called him by phone - facing him with what he just found. Needless to say, the person had no good explanation, and he was so terrified that he promptly removed her off of his friends list. Problem solved but this still scares the hell outta me.