I think open forum voting and no defined evaluation criterea already established the nature of the challenge. It is what it is. Any prize-induced subversion would be limited to either people who thought they could win and were willing to do so at any cost, or those who wished to skew the results. I don't think either of these types are represented here to any real extent, and even if they are, they were gonna throw a monkey wrench in whether there's a prize or not.