[imtringued]

Google isn't doing the race thing. They just pay out to whoever submits a valid submission. The people doing the racing are the submitters who want to get ahead of their competition and are stockpiling their exploits. If they were altruists, they would just submit their exploits for no renumeration. Hence the race isn't something Google is doing.

The proof of work isn't there to add a "four second race". It's to prevent ddos like spam.