Most of the maps used with Leaflet.js maps are based on OpenStreetMap, a freely editable and freely usable source of map data. Although major companies such as Google and Microsoft produce maps, free information gives OSM an unparalleled level of detail and customization.  This year, Google has begun charging many of their Maps users, and has convinced several sites to switch.

Recent Developments

In the past few weeks, Foursquare announced they would be switching to an OpenStreetMap layer from MapBox.  Then Apple switched maps on iOS's iPhoto app to their own system, partially based on OpenStreetMap.

#switch2osm movement

Follow the #switch2osm hashtag on Twitter https://twitter.com/search/%23switch2osm to read about other websites changing over, and read http://switch2osm.org/ to see why.

The Future

Will OpenStreetMap catch on? An apt comparison has been made to how Wikipedia's free-form, freely-editable articles displaced the Encyclopedia Britannica and Encarta. It was free-er, it was cheaper, and it made sense.

Major obstacles to OpenStreetMap include: no satellite maps or Street View, directions are difficult to set up, and fewer businesses are represented. OpenStreetMap requires you build sites and services on top of it, instead of relying on an API (like Google's).