Consider how much real achievement we would see if all the motivated hackers put down WoW and started up their development environment of choice.
But there's a lot of truth to the fact that human beings need recreation. We need down-time when we're not building, making, doing, etc. There's a lot of engineers who, if they put down WoW and fired up Eclipse would just stare at the screen for hours wondering what to build next. Or they'd disappear into an equally "unproductive" passed time like email, solitaire, or social news forums like this one.