Originally Posted by
OzPhoenix
Because you're not allowed to share accounts. This means for example, that I can't have someone else play my characters for me when I'm at work, to, oh, say, level 'em up, or say, oh, sell my account on Ebay and have some random Joe Schmoe play it from here on out.
So, if a Blizzard GM sees a bunch of synchronised characters running around in the world - a clear sign they're all being played by a single person - and checks the account information and finds that the accounts owner information don't all match, it's out with the banhammer for them.