Precisely. If you're offering any type of merchant services (and Gox does), then you already have to monitor all incoming transactions. All this means is that

Precisely. If you're offering any type of merchant services (and Gox does), then you already have to monitor all incoming transactions. All this means is that you have to keep a small list of the addresses of people with pending withdrawals, along with the corresponding Gox outputs, and then remove those addresses from the list as each block rolls in (at however many confirmations they determine they need).