So, now mojang is banning minecraft accounts that have migrated to mojang quickly and changed the password, email, etc.
SO, this means they monitor when that happens and will ban any accounts that look suspicious. Now if I were to buy an account and secure it as my own, I would have to leave the username [in-game name] and password the same, but change the email [locking the owner out] to a copy of it, such as: