Dredging up an oldie but a goodie...

All rulesmakers should take a half-hour and listen to this podcast. It really hits home toward the end...

The Cobra Effect

http://www.freakonomics.com/2012/10/...radio-podcast/

I think you start by admitting to yourself that no individual, no government, is ever going to be as smart as the people who are scheming against you. So when you introduce an incentive scheme, you have to just admit to yourself that no matter how clever you think you are, there’s a pretty good chance that someone far more clever than yourself will figure out a way to beat the incentive scheme.