"The blue markers ('community maps') indicate relevant user-contributed results for your search. You can click on the 'see more community maps' link either in the community box or at the bottom of the page to see more user-contributed results," explains Google.
Google includes in the search index all the public personalized maps, but also geolocated content from the web: GeoRSS feeds and KML files. So you'll be able to find Flickr photos that have a public location or news from topix.com. The index is far from being comprehensive, so it would be nice to see in Google Maps all the content from the web related to a location: photos, videos, news, blog posts, events.
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