Of course, these people know how to map their own mapping exploits.
The U.S. OpenStreetMap community gathered in San Francisco over the weekend for its annual conference, the State of the Map. The loose citizen-cartography collective has now been incrementally mapping the world since 2004. While they were taking stock, it turns out the global open mapping effort has now mapped data on more than 78 million buildings and 21 million miles of road (if you wanted to drive all those roads at, say, 60 miles an hour, it would take you some 40 years to do it).
And more than a million people have chipped away at this in an impressively democratic manner: 83.6 percent of the changes in the whole database have been made by 99.9 percent of contributors.
These numbers come from the OpenStreetMap 2013 Data Report, which also contains, of course, more maps. The report, created by MapBox, includes a beautiful worldwide visualization of all the road updates made as OpenStreetMap has grown, with some of the earliest imports of data shown in green and blue, and more recent ones in white. You can navigate the full map here.