Just a thought, but what would happen if you signed up on a forum with a username, made your posts and everything was fine. But then you Google'd your username and found out there were other people registered with your name on other websites. Could this have potential legal repercussions, if the post-loop member said personal information about themselves, and the other people using the username found out and decide to take the matter to court for impersonation?
Unless you own the trademark to the name, then there's not much you can do about it legally. If they're copying your posts too, you can file a DMCA complaint against them, as that is a copyright violation.
I see, I was just wondering what would happen if you used a username that has already been used on the net. I was wondering if anything legal could possibly happen. Thank you for the advice Pete! (by the way, I sent an email to postloop about this, please respond to it if you can)