It’s too early and I’m not bright enough to really understand this, but it seems very clever.
“…Eric Fischer, a 37-year-old computer programmer from Oakland, Calif., created a map using geotagging data on the photo-sharing websites Flickr and Picasa to plot the points in New York (and 71 other cities) captured by shutterbugs. He then devised an ingenious system for separating tourists from locals. A user with many shots of the same city taken over a wide range of dates is deemed to be a local, and marked on the map with blue dots. Tourists get a red dot. (Yellow dots could not be placed in either camp)…”
(Data Shows Where Locals, Tourists Snap Shots of NYC - WSJ)