Recently, at the suggestion of a fellow gamer here at Amazon, I read Cory Doctorow's book For the Win. It may not have been a monumental novel story-wise but it sure made some very interesting points when it comes to gaming economies.
Real life currency is, in fact, a shared illusion of confidence. There is nothing of actual value that backs the worth of a dollar or a euro printed on paper (in order to be an acceptable exchange for a portion of your life spent working) other than the confidence that, in turn, it can be exchanged for other goods. A rising inflation is a good example of how this confidence can be shaken and the value of what you have saved up greatly diminished overnight.
Modern economies are obviously virtual even at the level of simple currency - let alone the trading of non-existent commodities.
Enter Massively-Multiplayer Online Games, the likes of WoW. There is an actual market out there for virtual gold and rare legacy items. People are willing to pay real-life money for such things. Hence the hordes of Third-World gold-farmers, melting in front of sweat-shop PCs.
The prices fluctuate, depending on the demand. A popular game with more gamers will have the value of its virtual gold and rare items increase, whereas a game that gamers abandon in droves will experience the equivalent of the Stock market Crash of 1920.
If you were wondering why so many Multiplayers are turning Free lately, this is it: they want to generate or maintain the critical mass required for their economy to thrive.
So, (A) there is real money to be made in trading virtual gold and items,
(B) the people brokering it will be making money out or nothing, and
(C) he who controls the value of virtual wealth will control the portion of your life you spent acquiring it.
Now the reason why Activision/Blizzard is trying to keep such a tight rein on DIABLO 3 activities should be pretty obvious. They care not about ...piracy or keeping the game gold-farming-free (otherwise they would simply ban trading instead of brokering it themselves!). What they want is to claim a large portion of the new virtual continent opening up and rule over it in a totalitarian way.
They want to create a virtual economy and then run it like a communist state, by controlling the supply and manipulating the demand. And confiscating the property of any dissident before exiling him without even a semblance of due-process.
Will you be working for this new State?