From AdAge.com Creativity -
"New York becomes a gameboard.
The boroughs of New York City become the playing field for a giant game of digital Risk, World of Fourcraft, a game conceived during Game Hack Day NYC 2011, led by NY hacking collective NY Hacker and sponsored by Riot Games.
Fourcraft requires players to log in to the game site and swear their allegiance to a specific NY borough. From there, they check into Foursquare to conquer various neighborhoods."
Mashable - "Clever Foursquare Hack Turns New York City Into a Giant Game of Risk"
Gizmodo - "World of Fourcraft Is a Land Where Risk, Foursquare and Google Maps Collide"