I have a long-standing interest in the economies (and cultures) of massively multiplayer games. There are a few things that really interest me about these systems, but a few of the major factors are that (A) they adapt much faster than a real economy and (B) the distribution/creation of goods does not have to follow real-world algorithms.
Of course, to economists, massively multiplayer games are something of a silver bullet. If only they could find a way to load them into their gun, they could really get some great research in!
But, like all games that have a "purpose", games that are economic experiments will pretty much suck. So economists grind their teeth.
To me, the cool thing is not the idea that we could study shadows of real-world economies. I'm of the opinion that such studies would be hopelessly damaged by factor B. It would be equivalent to calculating the optimum approach for the space shuttle with a high school physics textbook. You know, the one that starts every question with "ignoring air resistance, we can calculate the..."
Instead, I'm a big fan of taking factor B and running with it. After all, as technology advances, our method of creating and distributing goods (and what kinds of goods) radically changes. The idea that technological advances are "more of the same, but better" is crap.
A cell phone is not "more of the same, but better" to third world populations. It's "this changes everything!" Similarly, vaccines aren't just "more of the same, but better" medicine. The combustion engine isn't just "more horses, but better". The gun isn't "a bow and arrow, but better". It may appear that way at first blush, but once it's out of the starting gate, it will finish the race before its predecessor even gets in one lap.
My interest is therefore in modeling the effects of this kind of advancement. Since a massively multiplayer game can more or less arbitrarily set the distribution and type of goods (and what those goods can do), I think it would be interesting to create a world to take advantage of that, and get some interesting data on how it affects things.
Specifically, I'm thinking of the idea of many worlds, each of which has different economic and technological underpinnings. For example, a post-apocalyptic world where technology is high enough that people can survive in small enclaves. A world of high fantasy and magic, where monsters run rampant and the economy is largely about how to travel and communicate over distance... a world of tribal plainspeople where gods exist and a major part of the economy is in sacrificing to them and receiving their blessings... there are a million possibilities.
One of the big problems with this is player population. It's almost impossible to guess how much population a game will have, and if you aim for a specific amount, you'll probably either never reach it or blow right past it. This idea of "gated worlds" would allow you to control the population in any given economy by allowing or disallowing players access: if a world is getting too hot, block new players from going there. If a world is too cold, make the player advantages of getting goods from that world higher. Add new worlds (even simple duplicates) as needed.
Of course, you'll still have the problem of a minimum player number you'd have to reach... you need the game to be fun and exciting enough to draw players in. Economies aren't fun and exciting as they stand.
The idea of a bunch of very unique worlds... that's pretty exciting. Especially if there's some kind of advanced crafting system and interpretive transitions: if you're a shaman moving from the tribal world to the future world, you transform into a hacker and all your shamanistic equipment transforms into equivalent hacker tools...
This creates a semi-permeable barrier allowing you to see how things flow between economies, and it also gives the players something really interesting to play around with.
Most interestingly, if you could figure out exactly how, you could actually allow the players to establish and back different kinds of economic models. Not just "pick and choose" from existing models, but actually implement entirely new models. For example, what about an economic model where copyright protects a work from corporate or government duplication, but not from individual duplication? What about an economic model where the primary currency is dragon scales, and they degrade over time? What about an economic model where data is completely free - no copyright, no government-assisted protection... if you can find it, you can duplicate it infinitely? What about an economic model where cash is backed by acres of arable land?
Anyway, that's how I would do it, if someone gave me a few million dollars of grant money. :D