The ONLY time we will take funds from your account that you received from someone is if it is flat our blatant fraud on your end. If the user who sent you money is able to do an chargeback on the ACH they sent us that is on us.
Awesome. So it sounds like TradeHill has nothing to worry about. But if anyone else is thinking "cool, a system where I can get payments with no chargebacks so my scam is good to go", they're going to get an unpleasant surprise.