The Nielsen Company released data for PC game usage for the month of March 2009. They based their statistics on the percentage of overall time spent with a given game. World of Warcraft is at the top of the list. No surprise there. But keep reading for a classic example of the sort of wonky data you get when you track the habits of a small group of consumers, as the Nielsens are wont to do. The chart lists Second Life as the second most-played game. Third is Dark Messiah of Might & Magic (pictured). Fourth is one of the expansion packs for Civilization IV. Not even the core game, which is 7th. Chessmaster Challenge follows shortly thereafter.