You might think that the image below is a map of North America population density. You'd be off by one level of indirection...
In fact it's a heat map of the access frequency for Virtual Earth map tiles.
So really it's not an image of where people are, but where they want to be...
The image comes from a paper out of Microsoft Research: How We Watch the City: Popularity and Online Maps, by Danyel Fisher.
Makes me wonder if there are tiles that have never been accessed. Like perhaps this one? (It took a looong time to render....)
And what is the most-accessed tile? This one, perhaps?
40 minutes ago