The article explains the details of the research, as the sample set was taken from gamerDNA users who have Xfire turned on. Within this research, we learn that 76% of users only play one title. Not surprising, that one title is mostly either World of Warcraft or Warhammer Online. To be relatively fair to WAR's newness, this research was done later than one month after the game's launch.
Where this analysis gets even more interesting is when we take a look at the cross-section of what types of players (between the one-game, or multiple-game players) are playing what games. Which games lend themselves to being more for the dedicated one-gamers, and which are typical for the multi-game crowd?