true fan: because it utterly devalues their investment - and the fans realise this. Rachel's CD sales suffer, Rachel's none-too-robust career suffers, and she takes another half-step towards obscurity. And the death of Rachel's career will mean the wiping-out of every fan's investment. And they cannot allow that to happen. Rachel Stevens is like a giant tamagotchi - fed by her fans, starved by the pirates. The more the pirates steal from her, the more the fans have to buy and buy and buy, until eventually their pocket money dries up, and Rachel dies. [emphasis in original] The BitTorrent peer-to-peer file-sharing system attempts to build robustness to free-riding by implementing a tit-for-tat-like strategy within its protocol. It is often believed that this strategy alone is responsible for the the high-levels of cooperation found within the BitTorrent system. However, we highlight some of the weaknesses of the approach and indicate where it would be easy to cheat and free-ride. Given that cheating of this kind currently appears rare, this motivates the question: why is the system not dominated by free-riders? We advance a hypothesis which argues that BitTorrent may resist free-riders in a way that has not been previously fully comprehended. Ironically, this process relies on what is commonly believed to be a weakness of BitTorrent - the lack of meta-data search. One consequence of this is to partition the BitTorrent network into numerous isolated swarms - often with several independent swarms for an identical file - which is one of