If the preceding paragraph makes no sense to you, you might be interested in an introduction to the Prisoner's Dilemma (trolled up almost randomly through Google), a facet of game theory which I believes explains almost all social interaction. Well, I exaggerate. But not by much.
another example of the prisoner's dilemma in real time
If you believe that the correct philosophy is to cooperate, not to defect, you might be interested in Swappingtons.