I purchased a few SoR accounts before and noticed some of the ones that got banned were banned before I even had a chance to bot on them. Then comes the email from blizz saying i'm banned for selling gold or blah blah. I'm starting to think that these SoR accounts that I purchased from these "reputable" sellers have used them as gold mules before actually selling them to others.. I could be wrong but what makes me think this is cause the person I purchased my SoR accounts from some of them already had a password that was set to their name already, strange. Anyways.. I've just beeing seeing alot of SoR bans lately and most of them are for expoiting gold selling or whatever. 
