[tomhunt]

karma would be the best thing, IMHNO. it has no monetary value, but can have social value. the "free labour" to your site is just that - free(monetarily, anyway). it has no monetary value in and of itself. as others have pointed out, once you do start to assign monetary value to it, then greed begins to naturally take hold and people just game the system even more. someone who is a frequent contributor on many sites, though - they tend to acquire rep - on the internet, no less, and will naturally attract all the things that a good rep attracts, which some would say is worth far more than money.

think of it like this - when you play a game of Monopoly, you're playing for play money. you get rich in the game, but the money you earn there is worthless outside of the game. at best you might earn some rep among your friends for winning (more than likely tho, they're a little pissed at you for screwing them in the game in order to win), and even that is pretty worthless outside of your social circle.

take the same game and play it with real money, and now it is gambling. see the difference?