It would also be interesting to slice this data in other ways, in addition to Fisher's clever tourist/locals divisions. For instance, what if we separated out the photos that were taken on weekends from photos that were taken on weekdays? Or map only photos taken between 9 pm and 3 am, to generate a diagram of cities' best nightlife neighborhoods? You could even go so far as to analyze the light and color balances of these photographs and generate maps of places where people go on gray rainy days, versus places where people go to photograph blue skies, versus favorite destinations on white snowy days.
In the meantime, both the Geotaggers' World Atlas and the newer Locals and Tourists maps are very much worth browsing, although, like me, you may lose hours to scrutinizing the richness of their information.