Snitch!: A History of the Modern Intelligence Informer (repost)

This is a vivid account of how some citizens actively assist state surveillance by 'informing' on others, such as during the Cold War and the current campaign against terrorism. With "Snitch!", Steve Hewitt provides a thorough study of human informers, i.e., people who secretly supply information to a domestic security agency (a spy provides information to a foreign intelligence service.)