Not long ago, being out in public meant being just another face in the crowd. Unlike at home or in the office, you could wander for hours and never meet anyone who knew your name or anything about you. You could walk into a store, browse library shelves, attend classes, and drive anywhere with near-perfect anonymity. You could pay cash for a one-way airplane ticket and simply disappear.

Those days are gone. Now when you walk into a store, a retailer can create a richly detailed profile of who you are, based on what you buy. The very items in your shopping cart can tattle on you, thanks to radio transceivers embedded in their packaging. Under the specter of the Patriot Act, the books you read and the classes you attend can become part of a secret dossier the government compiles about you. You can no longer fly anonymously, and soon you may be unable to drive without a tracking device recording your movements. Fear of terrorism has turned airports into armed checkpoints where you can be stopped and frisked at any moment for virtually any reason. Your most private medical records can be shared with literally thousands of others—legally, without your consent or even your awareness.

Your credit records are routinely swapped like baseball trading cards between a morass of interconnected banks, brokerages, and insurance companies. Get stopped by a cop? Better be ready to hand over your ID, even if you’re nothing but an innocent bystander. Even walking down the ...

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