It could be either money or a free entry in a contest. Whichever the player wants.
Since it is human nature to be motivated by rewards, I bet the added incentives would increase vigilance by the contest participants, and deter possible schemes (the way a thief will skip trying to steal in a neighborhood that has a Neighborhood Crime Watch there).
You could also include a reward for someone who finds mistakes in the software (as I did twice this year in the Cutline and never even got a thank you).
However, while thank yous are important, financial thank yous are way better.
