The rapid development of interesting web services can be attributed to the ability of each successive builder to create a layer upon what others have built. The existence of APIs and callable web services means that each builder can add value on top. When you combine this with crowd-sourcing, you effectively pour lighter fluid (in a good way) on this layering process. The only remaining element required is a taxonomy to insure that the crowd-sourcing creates content that is structured enough to make sense despite coming from many hands. PublicEarth , a Polaris portfolio company that is launching today, takes the power of API layering, crowd-sourcing, and taxonomy and focuses it on maps. PublicEarth describes itself as a wiki of places, specializing in collecting all those “long tail” places that most other databases tend to overlook.