Americans now enjoy vastly more privacy than in the past. But privacy makes it difficult to know much about other people; more privacy means more strangers. The Costs of Privacy begins with these questions: How, in an anonymous society of strangers, is trust possible? What enables both individuals and institutional actors to trust others whom they have never met and do not know? Nock suggests an answer: that surveillance establishes reputations, and it is these which permit us to trust strangers. Simply put, actors are willing to trust those whose reputations justify that trust. Not only does surveillance establish reputations, but it also maintains them among strangers. Nock defines such surveillance functionally, as overt and conspicuous forms of credentials (e.g., credit cards, educational degrees, drivers' licenses) and/or ordeals (e.g., lie detector tests, drug tests, integrity tests). He shows that the use of credentials and ordeals, over time, is correlated with the number of strangers in our society. Anonymity, then, is one of the costs of greater personal privacy; surveillance is another, offsetting cost. Older methods of surveillance have long been staples of our society. The concluding chapter focuses on newer methods of surveillance, those which can record genetic and biochemical information about people. Unlike traditional bases of reputation, genetic information makes it possible to predict future physical illnesses, mental health problems, and various types of behavior. These new forms of surveillance may seem attractive because they make it possible for actors to enter into risky relationships with many more people (i.e., trust them) without ever getting to know them. In so doing, we may be altering the nature of our public life. And that, argues Nock, may be the greatest cost of privacy.