Vernor Vinge made a similar prediction way back in 2006 in his book Rainbows End (no apostrophe), where "public health hobbyists" used public data to discover epidemics ahead of government agencies -- a DIY version of Google Flu Trends.
And in Halting State, Charlie Stross wrote about a role-playing game called "SPOOKS" that turned out to be a front for real spy agencies: when players went on missions to surveil what they thought were other players, real government spies were using the players' videos to collect real intelligence. It may sound implausible that people would run around taking pictures as part of a game; but in 2004, players of the Alternate Reality Game "I Love Bees" collaborated to answer 40,000 payphone calls [pdf] in 50 states and 8 countries.
Returning to North Korea -- it's worth downloading the map (you'll also need Google Earth). I spent a lot of time clicking on the list of "unusual" sites. You'll see strange towers in the middle of nowhere, huge patterns of earthworks, and mysterious geometric structures. Each location probably has its own quotidian explanation, but it's fun to speculate.