Finding a restaurant can be one of the most vexing tasks in modern life and an extremely useful application of Google Maps is getting help locating nearby establishments. The map below shows the number of user-generated placemarks containing the word "restaurant". The density of restaurant references corresponds closely with the distribution of population in the United States and Canada. In particular, the densely populated Northeast is blanketed with New York City containing the largest concentration.
When user generated placemarks are compared to regular Google Maps directory listings one sees essentially the same pattern of clusters, albeit and a higher density. For example, the largest number of directory listings of restaurants (again in New York City) is about 25 percent higher than user generated ones. Moreover, more rural areas (see the eastern U.S.) clearly have a high number of directory listing relative to user generated ones.
This suggests that user generated placemarks are biased towards urban areas where early technology adopters are most likely to dwell and use.