I suggest you guys be careful. First, this is mostly a scam - I've got access to few underground forums as for WOW exploits and such and on none of them there's a whisper of a dupe bug. However, if it managed to be true for some reason, it will get fixed in no time and the users will get banned regardless of on how many accounts you're going to do it, WoW logging system will trace it back to you anyway.