Another interesting web map which shows heat map of Panoramio photos – Sightsmap. This web map is based on Google maps api and the hottest places links photos, streetview, wikipedia, wikivoyage, foursquare etc. The heat map shows how many photos is in a certain place. It is example how huge amount of open data can be visualized with help of map and cartographic expression.
It would be interesting to see back-end of this map, how big data can be visualized on the web map, how to optimize this process. Also – how it is implemented the process of data update.
Maybe you have more examples like this?
Discover popular sights: the dark and the blue areas on the heatmap have few photos, the red areas have more and the yellow areas have a large number of photos geotagged.