Nobody is truly anonymous.
Besides, who can guarantee that the name somebody has given really is the person's real name. I could be Turd Ferguson from Orlando, Florida for all you know.
Besides, I'm certain it prevents a lot of conflicts if people are known by their real names.
And speaking of sigs, I think people should put their first name in their sig if they don't use it in their nick. I'm terrible with names and that way I won't have to remember them.