User-Generated Content on Google Maps
Google has started to integrate user-generated content on Google Maps. A search for restaurant stuttgart, for instance, first shows Google’s normally aggregated results (which Google says include “information from our web search results, data submitted directly by local business owners, and sources such as publicly available Yellow Pages directories”).
Below these links you’ll see the link “See user-created content,” and clicking on it switches the red placemarks to blue placemarks. I’m not perfectly sure where this data is from – for this sample search, GoYellow.de is listed – but it might be aggregated from public KML or KMZ files, as well as custom maps created with the My Maps feature. (KML is the Keyhole Markup Language, an XML file format to store location infos and more, and KMZ is just a zipped KML file.)