An MIT map of AT&T cellphone calls [via Gizmodo] reveals something about the interconnectedness of U.S. regions.
This constant flux of people commuting, migrating, and travelling across the country establishes connections which are dominated by large cities. The social connections woven across the United States can be used to define communities, where the glue that holds a community together is a stronger relationship with other members of the same community compared to members of other communities.
The team created a similar map some times ago for the U.K.:
