A world where everyone knows everything about everyone else has been a common dystopia. The villain in these frightening worlds has often been a shadowy government, thirsting for information and control. And that remains a frightening possibility in many parts of the world. But there are other, less gloomy outcomes. A world without secrets might actually yield a more forgiving culture with stronger, more informed individuals.

Citizens of the developed world now give off information about themselves at unprecedented rates. Authorities demand information from us when we fly, pass through tollgates, cross borders, and enter public buildings. As the investigation of the July London bombings has revealed, dozens of cameras may capture a city stroll. The cyber trails that people leave are now well known. As many have discovered to their chagrin, records of e-mails sent and Web sites visited rarely disappear—and they often pop up at the most inconvenient moments.

It’s ironic that the Web once seemed to promise individuals new opportunities to explore the world without showing their face. Instead, it is turning out to be a powerful force against anonymity. Most information about people’s online actions is traceable—if someone with resources cares to go to the trouble. But there will be much more to this trend than the familiar fear of governments spying on innocent victims, or even they-asked-for-it dissidents. The bigger questions revolve around the tolerance of societies for diversity and recognition of the human capacity for change.

The technologically adept and dedicated may be able to preserve some form of anonymity—for a time. Some people, for example, will create multiple identities online for the various sites they visit, the social networks they enter, and the...