Book excerpt: The new radically social habit of tracking our behaviours and preferences is booming. From Facebook timelines to Google Navigator to Twitter, we generate enormous amounts of online data about our activities: where we go, what we do, how we feel. In The Virtual Self, journalist Nora Young examines this growing phenomenon of self-tracking - why it's compulsive, its attractions and benefits, the dangers surrounding privacy and information control, and moreover, what it means for our sense of self. Fascinating and entertaining, and offering unique insights into our emerging technological culture, The Virtual Self takes the personal, psychological reality of everything from smart phones to social networking and teases out the increasing impact of the virtual information we all produce on the real world around us.