A study in which researchers secretly tracked the movements of 100,000 people through their cell phones is raising eyebrows in privacy circles.

The research, done by the Center for Complex Network Research at Northeastern University in Boston, is published in Thursday's edition of the journal Nature.

The research was done outside the United States, where such monitoring would be illegal, in a site identified only as an industrialized nation in a story by The Associated Press on MSNBC. It also required the cooperation of an unnamed private company, which The New York Times describes as a European cell phone service provider.

Basically, it found that people rarely venture outside their routine movements, making them pretty easy to find at any given time. That would seem pretty obvious, but the researchers say the work has potential benefits for use in disease tracking and urban planning.