Foursquare, which I thought was still a location sharing app but is a data platform now, open sourced a layer of 100 million points of interest in an effort to build and maintain a global database:

[L]et’s now consider the challenge of creating and maintaining a real-world-synced place database. As our CTO Vikram Gundeti detailed in a recent blog on our newly re-launched Place Engine, to do this well requires an operating system powered by human-in-the-loop confirmations harmoniously orchestrated with cutting edge digital discovery systems to actively curate a database representative of the current world. In short, building an accurate global database of POI is an extraordinarily difficult task both from a technical perspective and from a capital resource perspective.

This leads to our belief that, absent a global proprietary distribution platform like Google Maps, building a comprehensive and accurate base layer of place data is indeed a problem best solved by an open source community.

You can access the dataset now.