Could it be possible for a person to register using a payed e-mail which was used by another person to register, if this last person was no longer using that e-mail, and they would both connect from different computers (thus not being multis)?
e.g.: Jhonny registers using his payed e-mail. His brother also wants to do so, but has no payed e-mail of his own. They both have a room with a computer, and Jhonny changed the e-mail in the account settings page to his gmail account.