I think this sums it up. By making the contests a little harder or by making them rely on skill rather than luck, it reduces the number of people that are able to complete the goal and increases the odds that those that DO complete it are able to win the prize.Originally posted by AmShak
The winner is drawn from the names of the people who are able to complete the game, which dramatically increases the odds of winning over the normal, "send us an email with your name" type of contests.
With a number of sites involved, the "Prize Pool" increases significantly as well making the search for the banners worth the effort.