Consider that even with zero confirmations, with enough clients validating and relying the transaction, it's pretty hard for an attacker to propagate a double-s

Consider that even with zero confirmations, with enough clients validating and relying the transaction, it's pretty hard for an attacker to propagate a double-spend for that transaction. This is where the big mining pools are actually a good thing. In a zero confirmation scenario you could send the transaction to all the big mining pools and wait till they see and validate it which could take just a few seconds. This way it becomes incredibly hard, even with zero confirmations, for an attacker to get her double-spend mined because the big pools saw your tnx first. For large sums of money of course it's safer to wait for many confirmations, but for $30-40, the risk is relative.