This sounds like fun..

I remember reading an article many years back from an economist who did his thesis on the MMORPG ecosystem..

He tracked the coin in one (possibly WoW) and compared it to how certain items were selling for money online. Compared them adn got a USD value. then estimates the total amount in the online world..

I recall it being something like 'larger than most small countries' or something like that..

Fascinating prospect.