Susan Sontag, On Photography page 19

The industrialization of photography permitted its rapid absorption into rational--that is, bureaucratic--ways of running society. No longer toy images, photographs became part of the general furniture of the environment--touchstones and confirmations of that reductive approach to reality which is considered realistic. Photographs were enrolled in the service of important institutions of control, notably the family and the police, as symbolic objects and as pieces of information. Thus, in the bureaucratic cataloguing of the world, many important documents are not valid unless they have, affixed to them, a photograph-token of the citizen's face.