Not a bad idea although it would take a very long time to make build any substantial cash amount but hey, look at the Nectar scheme, it cant be any worse than that.
The only disadvantage to such a scheme is that whilst people may spam it may also result in people talking about absolute rubbish such as what they are having for tea etc..I may even have been guilty of it myself for the past few weeks in attempt to keep things ticking over on the threads
Anyway, how about introducing a recommendations scheme where posts are given recommendations.
I see you already have something similar in place but not in conjunction with the v chips.