Reading the Truebit white paper I see parallels in this statement:
As an example of the second type, consider a situation where the Solver deposit is small (say 10 ETH) but the expected jackpot payout per task is high (say 1000 ETH). An individual playing both the role of the Solver and Verifier could offer a bogus solution and then challenge his own answer, hypothetically netting, on average, 1000 − 10 = 990 ETH without providing any useful service. Such an action would degrade other Verifiers’ incentive to participate.