The best thing about these kinds of contests is they draw all the cheaters & alt accounts, making them easy to identify.
I know the contests are born out of purely good intentions, but as we've also seen with the pizza and art contest (as well as all the price prediction contests & free raffles), they attract a lot of users without consciousnesses. Anything that has to do with free money will attract scumbags who won't respect the rules -- that's just how its always been, long before bitcoin.
Some people are also attracted because of the merits received from joining the contest. I know that many forum members know this that many of the participants receive merit joining the contest. I am also participated in a contest before to have fun while doing what I am going to submit either I receive a merit or not. Well, most of it are about earning free money as you have stated that people who are cheaters will do what they do best and that is to cheat.