"There seems to be something about the content that significantly changes how your monetization occurs, with apparently much broader participation than you would see out of something like FarmVille." When Team Fortress 2 relaunched as a free-to-play title back in June, the title's user base increased by "a factor of 5," which Newell attributes to TF2's designation as "free-to-play" rather than simply free: "You have to start thinking about how value creation actually occurs, and what it is that people are valuing, and what the statement that something is free-to-play implies about the future value of the experience that they're going to have."
Hey Valve, wanna know the secret? It's the hats. People love hats.