Once upon a time the folks at Blizzard Entertainment thought they could support the entire world of World of Wacraft by ad revenue. This would have created an MMO experience which would cost you nothing but a bit of annoyance by ad providers; what would the total audience be if the game was free?
Had WoW launched free of charge they would probably have significantly more users playing the game, but the ad revenue from the sheer amount of people would be nothing compared to a monthly charge for eight million subscribers.
Although only a small number of those subscribers are US based, they’re still raking in the cash compared to an ad-based model, even if they were to have triple the subscribers.
However, the Blizzard exec noted: “We didn’t want to charge a subscription, but as we researched market conditions, we realized that wouldn’t support us.”
It’s possible, perhaps, that Blizzard would have fallen under its own weight had they created a world where anyone could play for no charge. Imagine the server utilization, the volume of traffic and the support calls they would get for triple or quadrupal the player base with only ads paying the checks.
Granted, a free system would be excellent in theory, but in practice, making us pay is the only way to throttle our addictions. Sad, but true.
(Thanks, gamasutra)
Now even Bethesda is saying 
UK developer David Braben from