This is an interesting tease. I'm not sure why they are teasing it (presumably to get developers) but conceptually from a game perspective it could be interesting.

I played World of Warcraft from 1.0 (actually 0.9 but whatever) to 4.0 (a bunch of years, I've got the pets to prove it :-) Felt it finally completely jumped the shark with the Panda thing and the simplification of the world to the point of banality. As I told the Blizzard guy who surveyed me about it, I don't go into the library at the Middle School to play DND with the kids there using rules they can understand, I do play complex scenarios with other adults. I think Eve Online gets this, Blizzard has yet to internalize it.

WoW was created to compete with EverQuest, which it did, way more successfully than even Blizzard expected. But it ran into the problem that the storyline, while interesting, and which character progression suitably nerfed, it got boring. And adding new story lines helped, but they had to add better gear to keep people grinding for it, and the basically I think they ran into the law of diminishing returns. Making your character twice as powerful was cool, but it made the previous game a bit silly, doubling that again and now you could single-handedly waltz through the old end-game raids (which had been designed for 40 simultaneous players in their best gear), and the dissonance gets to you. It's kinda fun, like God mode, but it's also hard to imagine a world where you could be this powerful and everyone else couldn't just fix the worlds problems without you. When the story line is "we're under seige by the forces of evil" and your character, through a series of quests, singlehandedly overwhelms all that evil? Its like reading Nancy Drew mysteries instead of Agatha Christie mysteries. To simplified to be enjoyable.

Then there is Eve Online, which is similarly durable to WoW and yet has a much larger percentage of retained adult participants. I expect for the reasons that Eve does not constrain the behavior and doesn't make it "digestible" to people who don't understand that money can buy power and power can be manipulated. Compare getting into a high end Eve Corporation with a high end WoW guild. Interesting difference.

And then there is the business model. Everquest, WoW, and Eve, all have pay-per-month subscriptions. That is nice, but Zynga and others have shown it can be just as, if not more, profitable for the company to run the internal economy. Something Blizzard shied away from on WoW, embraced on Diablo 3, and Eve has had I think a mixed relationship with (but I may be completely wrong on that I'm not as familar with the online Eve currency market)

That suggests that there may be a market for a persistent world, with 'stories' for interest but not necessarily character gain, an environment where you every bit of content is available to you (perhaps not as successfully as you would like) from the moment you log in, and where you can use economic means or game-play means to achieve goals. Combined with a system for mixing up character strengths, items, and what not. With the game company running the economy, and taking a tax on that economic growth to fund the actual game. You have to be willing to bet that for everyone out there who will diligently cut rocks or what ever for a .001% chance at a powerful gem, there will be 10, 100, 1000 people who will just fork over fifty cents to a couple of dollars to just buy one. And playing the average revenue per gamer game rather than the monthly fee model.

Bootstrapping something like that will be extraordinarily hard, but if successful consider how much Blizzard would have profited if they had been the 'gold farmers' which at one point was estimated at a several hundred million dollar a year business in its own right.

Tending something like this, keeping it fun and profitable will also required very deft execution since it is tempting to take too much money off the table early on.

I hope the Bungie guys pull it off.