This was the paper that started the ongoing growth of academic and business interest in the virtual economics and real-money trading on virtual, game property:
Castronova, Edward (2001) ‘Virtual Worlds: A First-Hand Account of Market and Society on the Cyberian Frontier’. CESifo Working Paper No. 618, December 2001. Online: http://papers.ssrn.com/sol3/papers.cfm?abstract_id=294828
An Introduction to Game Studies 