> If the exchange is aware of the attack, they may also freeze his account, so that all the funds will be locked inside the Exchange. A failed 21 block attack performed with a 10,000 BTG deposit where the Exchange freezes the account in time will result in a 10,262.5 BTG loss for the attacker. (From link.)

That sounds problematic. If I deposited coins and the exchange determined I was attacking them (how does that work beforehand?) to confiscate my money I'd be pretty miffed.