From PBSoffbook:
While players of multi-player games are aware of their in-game economies, their growth and complexity would surprise many outside the world of gaming. With hundreds of millions of players around the world, MMOGs’ in-game economies generate massive amounts of real dollars (i.e. MILLIONS), and real world economic theories can even be applied to these worlds. Many are now so big that game developers have hired real world economists to help them manage these complex systems. But with secondary economies, gold farming and other issues surfacing, are these systems in need of more attention, or even regulation?