The Money Trail

Via J.A.D.: MedPage Today reviews a Nature article about tracking people by their money:

The model is based on an analysis of data collected by a popular Internet game -- found on the Web site www.wheresgeorge.com -- in which participants enter the serial numbers of bills in their possession.
Over time, as different people enter the same bill, the game builds up a picture of how the money is moving, said Dirk Brockmann, Ph.D., of the Max Planck Institute for Dynamics and Self-Organization here.
But since paper money -- like viruses -- travels with people, the game also allowed the researchers to model how humans move through the world, without actually tracking them, Dr. Brockmann said