Are you quite wealthy?

You could have been banned for sending large amounts of money from one of your toons to another?

We've had a thread about this before, but trading large amounts of gold (idk how much, but probably over 100k) to someone in one trade will trigger their red flag. So if you were moving gold between your toons, Blizzard's alarm could have gone off, and since they are too busy to ask you directly wtf just happened, they handed out the ban.