This essential volume considers the importance of privacy in the digital and post-9/11 era. Essays are presented that represent divergent viewpoints. Viewpoints debate the extent to which privacy is necessary, which measures most effectively protect privacy, and how best to balance privacy with national security and other critical issues. Facebook, full-body scanners, I.D. cards, and the constitution are among the topics. Essay sources include Janet Napolitano, Tim O''Reilly, Jeffrey Rosen, Mark Scholosberg, and Nicole A. Ozer.