World of FourCraft
“World of Fourcraft” uses Foursquare and Google Maps APIs to turn New York City into a giant game of Risk. Users decide which team they are on by swearing allegiance to one of New York City’s five boroughs. Checking into a neighborhood on Foursquare is the online game’s equivalent to placing plastic man on a country in the board game.
An algorithm decides who owns each neighborhood using the number of people who have checked into it on each team. There are currently about 100 players.