To clear up some confusion on BANNING: : World of Warcraft General Discussions

When a CD Key is used for account creation, it states that the CD Key will be invalid for any more accounts. This means, a one time use only on any CD Key you purchase from the all so almighty Blizzard Corp. If/When you get banned, that means, that the account is banned, and the CD Key doesn't exist anymore. So when they erase all of your information off of the account, the name of the account stays, and the Key is no longer circulated into the Blizzard products, (so blizzard can make more money).