Routing 30,000 randomly-chosen trips through the paths suggested by 10,000 randomly-chosen geotags. These are perhaps the most interesting routes between the endpoints of the trips, even if not necessarily the most likely.
Data from the Twitter streaming API, August, 2011. Base map from OpenStreetMap, CC-BY-SA.
http://www.flickr.com/photos/walkingsf/6755895487/in/photostream/