As we live our lives, we leave behind a vapor trail of information: the places we go and how fast we get there, the people we talk to, the stores where we shop, taverns where we drink, churches where we pray.
Powerful computers in our purses and pockets are now recording that data. The cellphone is not just a communication device; it is a diary. And with the data from millions of these diaries, businesses,
government agencies, and scientists are learning how to forestall medical crises, identify emotional problems, prevent the spread of infections diseases, or simply sell more pizza.
Haiwatha Gray in the Boston Globe about the profiling of cellphone users