Incentives Build Robustness in BitTorrent

This is a link to an excellent short paper by the creator of BitTorrent, Bram Cohen.

It explains the technical detail of the inner workings of Bit Torrent, and the relationship to economic theory. The upshot of this is that although BitTorrent clients can be written by others, the system as a whole is designed from a point of view of not trusting other peers to do the right thing (unlike previous popular file sharing programs like Kazaa). Instead, peers reward other peers that cooperate, and punish those that don't. Thus, it is an extremely robust decentralised system. Brilliant!