[mmacaulay]

Reputation and other points systems are designed to attract people because it's like a game - in fact, this very site uses it!

Obviously there's the problem of people "gaming the system" to earn more reputation and you do whatever is possible to prevent that, but there's no reason why people can't be there for both the reputation points game AND to spread knowledge. The problem now for Stack Overflow (as I see it) is that it's reached a level of saturation where it's difficult to do either.