In each of these three examples of situations where personal privacy may be invaded, there exists a strong argument for doing so in the name of the common good – for prevention of epidemics, for prevention of crime, and for prevention of traffic accidents. They differ fundamentally from the currently familiar arguments for invasion of our data privacy by law enforcement – for example, to read our email or to look for evidence of copyright violation. Reading our email involves our public and private speech, and looking for warez involves our public and private assertion of intellectual property rights …. but eavesdropping on our metagenomic environment and our sensory environment impinges directly on the very core of our identities.