My team and I did an analysis on our Facebook dataset recently that might (or might not) have inspired this particular work.

You can find the geographic analysis within this blog post:

http://blog.stephenwolfram.com/2013/04/data-science-of-the-f...

There is a much higher resolution version of the "migration wheel" available here:

http://www.wired.co.uk/magazine/archive/2013/12/start/facebo...