I brought up this study in the past within a broader discussion of urban convergence and urban edges. They've expanded the amount of cities represented to a metric sh!t-ton and now distinguish between locals geo-tagged photo uploads and the path between pictures.
Here is Dallas. I downloaded and reframed to focus on the city core. See all of the cities here. Clicky on the picture for the zoomed-in version.
Blue is for locals. Red is tourists and yellow is for the lizard people (or the indiscernible anyway which isn't nearly as fun).