Andrew made a good point above: the big risk of setting up gaming systems to motivate real work is that people will optimize for playing the *game*, not doing the *work*, so you had better be very thoughtful about whether your rules encourage the kind of behavior you really want to see.

It reminds me of the old story about the company that decided to pay its developers a cash bounty for every bug they fixed. Hmmm, let's see - code up ten bugs, check them in, fix them the next day . . . easy money!