Hiya,
as far as game economies go, I think in many ways that the simplicity could actually be an asset. I stress here that I'm not an economist (although it does interest me as a suject), but with economics you often have to make number of assumptions that aren't completely true. An assumption made for certain simple economic models, for example, is that goods can be homogenous.
In real life this isn't the case, but in an MMORPG, it is. This means that you could study MMORPGs because in many ways they operate under some of the assumptions made for economic models. It might be possible, for example, to monitor an experiment whereby you could assume perfect homogeneity of goods, as well as perfect information in the marketplace. You could then see whether Marx's economic theories or Smith's were closer to the mark in this set of circumstances. Because the same map is being run maybe 30 or 40 times with different servers and different players present, it means that the experiments are repeatable.
Also, markets are often player-driven. Studies of EQ2 showed that you could use models (that took into account variables such as geography, war, demand and supply) that are used in real life to predict, reasonably accurately, where player markets would appear.
I completely agree though that there are differences, and that studies would have to be carefully tailored to each different game. There's a limit to how far you could take this approach, because your right, game markets are different.
I think you raise a good point about violence in games. But I think often when we use the word violence, we refer to physical violence. I would probably describe a James Bond movie as being more violent then an episode of a soap, say, even if the soap contained more verbal abuse.
I would argue, though, that WoW encourages an aggressive physical response towards the environment in gameplay. In this sense, it has violent elements. When you go into a dungeon, you often will have to band together because if you don't, your character will be attacked by monsters. The environments you travel in are often hostile, because creatures will often behave aggressively towards you. This encourages group interaction because players band together in reponse to this to triumph over the environment. I think Second Life will be interesting because you don't always have that environmental pressure caused by the threat of in-game physical violence against your character. Maybe players will band together against verbal abuse instead, as shown in the news article above.
I seem to have gone on a bit. Sorry, I do enjoy a good debate.