It has been a truism for some time that GIS enables us to build models of the Earth. Esri Press has even offered a book on geodatabase design called “Modeling Our World” for a while. Traditionally, GIS has given us the ability to model the surface of the earth (in a broad sense), including our effect upon it. That can be extended to subsurface modeling and weather modeling and similar concepts but, in general, GIS has focused on the surface of the earth, plus or minus a few thousand meters or so.
I read with interest this article that was brought to my attention by @gis_Todd on Twitter. I have been playing with Foursquare for a few weeks now and I think this article is in sync with some observations I have had about it but also misses the mark on one key point.