The problem with programming challenges is that if you win a programming challenge, you probably could've spent the same time doing a very similar thing but produced something of much greater value (money, software that people will actually use, research that will actually be built on). The unfortunate consequence of this is that you aren't likely to see many rationalists entering these competitions without strong motivation, and a little prestige and publicity isn't enough.

Also, building a functioning team of programmers out of loosely-committed geographically-dispersed acquaintances is ridiculously hard, and if you could do it, you wouldn't waste that power on a game.