You've been selling gold or other item ingame for real money. I got one a couple of days ago, but I had not been selling gold (yet), so I emailed them and asked the to lift the ban on my account. Then I waited 4-5 hours, and the ban was lifted
Or you raged at the auction house selling thousand of auctions every day. Therefore you will get banned too.
Okay ive been unbanned now but the only thing i did was seelling all my herbs in the AH after ive botted herbalism 1-525 ^^
yeah then they thought "hey this guys sells xxxx stacks of herbs...must be a bot user" and bam ban. I would suggest only posting <500 auctions per day.
got a suspension on one account today too for this reason. after appealing it got un-suspensioned. it was a account that i only quest-botted and did some auctions... cloth and this crap...
got a ban today to (72h) , abuse of economy. dont have any auctions or traded any gold, but i put up a appeal and hope the remove it