What makes a world different from a game?

Virtual world research Edward Castronova reflects on Star Wars: The Old Republic failed to attract enough paying customers, while EVE Online continues to thrive. The secret is context and design:

What makes a world different from a game? Well, in a world, there’s downtime and exploration and life. Downtime is, moments when there’s nothing to do. You just be. And it is nonetheless interesting. Exploration is, you go places simply to see things, to discover them. You don’t get a reward, you just go look. It’s a cave with artwork in the bottom, and nothing else. It’s a desert to cross, in which there’s an oasis with a palm and an interesting little bear who sings rhymes. And nothing else. Life is, when you go to a place and there are people just being there. They’re not on a quest, they’re not grinding a craft, they’re not shopping. They are simply being.