How can someone else use my name?

Ok, so I decided to try this thing out. The weird thing is that when I tried to sign up for the username "riddler" it was already taken. But if you go to that journal, it's not even being used. How can someone else use my name for a username? It's mine dammit! It's just not fair. I also tried riddle_me_this, theriddler, and a variety of such combinations. So now, I am riddleita, the little riddler so to speak.So here begins my live journal...yet another reason to be chained to a computer all day long. For you old-timers, any recommendations?