I like to add to any discussion of Prisoner's Dilemma a similar note, something like: This is why contracts matter. It's clear that both parties would love to

I like to add to any discussion of Prisoner's Dilemma a similar note, something like: This is why contracts matter. It's clear that both parties would love to sign a contract saying "I'll scratch your back and you scratch my back," if the consequences of not obeying that contract were sufficiently severe, because they see that they can get a mutually better reward. The reason why criminals do better than game theory professors on the prisoner's dilemma game is not necessarily because they act irrationally, but because they're part of a social order which creates and enforces those sorts of cooperative systems, and which doesn't do business with folks who break them.