People here obviously haven't read the rules. As soon as some GM gets on and starts going "RAWR YOU BE USIN' SOMEONE ELSE'S ACCOUNT!" reply with a simple "Yeah, I bought it."

Perfectly legitimate. Buying and selling accounts is legal if all of the contents of the box are transferred to the new owner. Obviously, a new account cannot be made with the CD key so the account also becomes property of the new owner. It doesn't matter whose name the account is in, so long as you can prove you are in possession of the retail box and you pay your fees, there is nothing they can do.