Andy Woodruff from Cartogrammar uses average color in Flickr photos to map the colors that people take the most pictures of. The above for example, shows the common colors of Harvard Square. Why all the red? It's because there's so many brick buildings.
So in the end is a map that provides a different geographic view of what we're used to seeing. We're used to seeing the aerials or the designer-defined color coding of roads and land. This however, while portrayed as a view from above, is what people are seeing on the ground.