Virtual item ownership has been a hot topic in MMO circles for a number of years now. Every so often, an academic will publish a paper regarding the legal and societal implications of trading real currency for fake goods, and the latest such academic is Rutgers University law professor Greg Lastowka
Lastowka examines a number of high-profile virtual goods disputes (including one that ended with the real-world stabbing death of a virtual thief who sold a rare sword after "borrowing" it from a friend).
The piece also provides some interesting food for thought in the form of nightmare legal scenarios run amok (nerf patch lawsuits and legal action for server shutdowns are just two examples). You can read the full article text at Gamasutra