I'd love to see coinbase's network traffic right now as this spreads through the net. I really wish coinbase would allow currency exchange from bitcoin to any currency (hint hint coinbase).
I remember one of the first algorithms I wrote was to pattern trade the exchange rates (USD -> CHF -> EUR -> DNK -> USD), but then I realized that the fees would kill any potential gains from the imbalances.
Incidentally, I transferred some BTC from MtGox to Coinbase when I heard this news. It might be safer to have it in my own wallet somewhere, but if there's no way to get BTC back into USD, it doesn't matter where the BTC is to me; I'd consider it written off.