This is a guest post by Ed Freyfogle, co-founder of the Nestoria property search engine: OpenStreetMap started four years ago in the UK as a project to create a free and editable world map. What began as a few geogeeks wandering the streets with their GPS’s has turned into a global movement with over 75,000 registered contributors. The database has improved rapidly in quality and comprehensiveness, as have the tools and services around it. OSM is becoming a viable datasource for complex projects. The project’s stats are another demonstration of the awesome power of a motivated online mob. The passion of some of the volunteers is shocking; there’s even a student attempting to go his entire time at uni using only OSM maps.