My oldest (11) has one and we monitor it closely. He is not allowed to friend anyone he doesn't know and he is not allowed to friend adults (only family adults). He honestly doesn't use it too much anymore. We have not yet allowed our younger 2 to have one.

personally I think it just depends on how mature your child is I know children who have gotten an account at age8 to stay in touch with family & I also know some 30 yr old who will never be mature enough lol

My son got a fb account when he was 16. I monitor it closely and have the password. So far so good, he is 18 now