Although I have little time to play it myself, I watch developments around Second Life with great interest. It's just too fascinating. The New York Times has a rather superficial article on the real world economics of games like these, but I really liked this quote about someone's second life that resembles his 'first' life.
"But Mr. Ainsworth found his moneymaking options in The Sims "very limited"; he switched to Second Life, a virtual world that is less a game than a three-dimensional environment in which players can do whatever they choose. There, he has leveraged his real-life experience - he is a developer and contractor - into an online business. In 14 locations in Second Life's virtual world, he owns enough "land" to rent space to nearly 50 retailers, who in turn earn virtual money selling everything from jewelry to clothing to art (all nonexistent, of course). Mr. Ainsworth converts his game profits into real money on sites like eBay, Ige and gamingopenmarket, which charge a small fee, and he includes that income on his tax returns."