He won't get banned for it, but he will be costing someone 10 ads to recover it. So, in the end, he gets nothing, and the guy who dropped the item will have to pay 10 ads because some players simply don't have the decency to give items dropped back.
Actually, I picked up an item that was dropped, and got charged for it after the item was recovered >_>
I don't think that should have happened o_o
@ Tonedeff - if he really was dropping things on purpose, then play around with the item till the GMs recover it from him (but don't resell it since that'll be unnecessary work for the GMs)
However, consider that he mighta been trying to trade a lot of items to Kafra, using a clip, or switching his equipped gears, and had forgotten to put up alt Q - in that case, he was just a bit careless, and for a simple mistake like that I don't think he deserves to pay up 10$ if you're capable of returning it to him without a fight.