I remember that one adult webmaster forum, uses their bucks as "currency". The bucks are used to buy services and advertisement spots from other members. And sometimes traded for real cash (with other members.) For example: member x gives y amount of forumbucks to member a, who then will give b amount of real money to member x.
That kind of system would be great to have here as well.
Note: I tried my best to explain the scheme as well as I could. But hey, you know me. My explanations suck: