Unintended Consequences

I just came across this post by Janet Stemwedel (alias Dr Free-Ride) in which she and her family attempt to teach their younger child how to 'work' a classroom behaviour reward scheme.  It is a wonderful lesson in economics and what Bruce Schneier calls the security mindset. 

That something apparently so simple can contain such complexity should be a lesson to politicians who want to introduce schemes such as charging for emptying bins.