Rights holders have been successful in every major copyright action brought against peer-to-peer (P2P) software providers. By 2005, those behind Napster, Aimster, Grokster, Morpheus and Kazaa have each been held liable for their users‟ infringements and effectively exited the market. But those successes did not result in any reduction in the availability of P2P file sharing software. In fact, the opposite occurred: soon after the U.S. Supreme Court ruled in favor of rights holders in Grokster, there was exponential growth in the number of P2P file sharing applications available. This Article argues that this came about because the pre-P2P and current U.S. secondary liability laws were and are based on a number of physical world assumptions that are simply not tenable in the software context. After identifying those assumptions, and contrasting them with the relevant software world realities, the Article demonstrates that the explosion in the number and availability of P2P apps can be traced directly to the Supreme Court‟s failure to recognize the mismatch between the two paradigms.