My god, these stupid Minecraft updates... If you chose a username, you shouldn't be able to change it to anything at anytime... Now a quarter of Minecrafters will lose their identity due to them being silly n00bs and changing the name of their main account. Thank you for the warning, though, I'll be sure to spread word that changing the username will erase every shred of data.
Two questions, thhough... If a banned person changes their username, is there any way to keep them banned besides IP banning? And also, if you change your username to one who already had a res, does that mean that it becomes yours? O.o