I am fascinated by the international community of volunteers who work together to put an end to internet scams such as the notorious "419" advance fee fraud.  

"Scambaiting" (i.e., the practice of thwarting the scammers) is not only moral crusade but a sport, a very odd form of interactive gaming in which the players pit themselves against alleged criminals. (For an extremely twisted example, see the Joe Japez/Robert Keller case.)

I've devoted a fair amount of time to learning about this, and have been rewarded with some extremely strange glimpses into human nature.  The more I reflect on scambaiting, the more Friedrich Nietzsche's admonition seems to apply:
He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss, the abyss also gazes into you.  (Beyond Good and Evil)