From this article where a journalist of The Observer immerges for one week in Second Life :

• Anshe Chung, Second Life’s richest avatar, owns a property empire on the site worth $250,000 (£137,000) and employs 17 real-life people.

• Second Life has an estimated GDP of $64m. Last month alone, $6.6m was spent in user-user transactions – 40 per cent of it on designer clothes.

• More than 3,000 residents earn an average of $20,000 in annual revenues from the game.

• Musicians who have played virtual gigs in Second Life include Duran Duran and Suzanne Vega.

• Possible 2008 presidential candidate Mark Warner was interviewed by a virtual journalist in a Second Life town hall.

• 20th Century Fox held a premiere for the third X-Men movie in Second Life and BBC Radio 1 recreated its Big Weekend festival on a virtual island.

• $1bn was spent last year on multiplayer games such as Second Life.

(…) “I’m struck, not for the first time, by the insane seriousness of this place. It’s clearly much more than a game. (…) He arranges to see Adam Pasick who works at the Reuters agency. Adam is the first full-time real-world hack in Second Life. In the lobby of the high-tech Reuters office Kenny runs into a Canadian TV crew working on a story about the story. (…) He’s been here two months now, he says, and he is starting to dream in RL about Second Life, which is alarming him. Since he is on all day he feels he should get his wife an avatar. He’s been madly busy, he says, breaking the story of US tax investigation into SL businesses.”