Easy hulkster. Alot of people register under new names just to play stupid pranks on other guys...I think Ranger used to do it all the time. They can't limit people to one user name, because you can just log off and register under a new name. There is no way to limit the amount of accounts that anyone has.
Thats what I was thinking. How would they limit people to 1 account? It doesn't seem possible.