Internet denizens and urban dwellers alike need to recognize that an era of anonymity is ending.
The population of the world stands at about 7 billion. So it takes only 10 digits to label each human being on the planet uniquely.
This simple arithmetic observation offers powerful insight into the limits of privacy. It dictates something we might call the 10-Digit Rule: just 10 digits or so of distinctive personal information are enough to identify you uniquely. They're enough to strip away your anonymity on the Internet or call out your name as you walk down the street. The 10-Digit Rule means that as our electronic gadgets grow chattier, and databases swell, we must accept that in most walks of life, we'll soon be wearing our names on our foreheads.
A study of 1990 U.S. Census data revealed that 87 percent of the people in the United States were uniquely identifiable with just three pieces of information (PDF): five-digit ZIP code, gender, and date of birth. Internet surfers today spew considerably more information than that. Web sites can pinpoint our geographical locations, computer models, and browser types, and they can silently track us using cookies. Banking sites even confirm our identities by verifying that our log-ins take place at consistent times of day...
Our physical belongings also betray our anonymity by silently calling out identity-betraying digits. Small wireless microchips--often called radio frequency identification, or RFID, tags--reside in car keys, credit cards, passports, building entrance badges, and transit passes. They emit unique serial numbers. Once linked to our names--when we make credit card purchases, for instance--these microchips enable us to be tracked without our realizing it.