They're certainly the currency within Second Life, but Linden Dollars (L$) can be bought and sold -- for "first-world" currency -- at several online exchanges. In other words, not only can you spend U.S. dollars to buy Linden dollars (in case there was something you wanted to purchase for use inside SL), if you earn Linden dollars you can cash them in for U.S. dollars. The exchange rate fluctuates around the region of L$300 to $1; at the end of the first week in January 2007, the Linden currency market (the Lindex) closed at 269.8. Rates are to some extent moderated and adjusted by Linden Labs, though SL's terms of service stipulate that the currency can't be redeemable for value from Linden Lab itself.

So it's just talk, walk and consume?

No. Second Life has hosted several cultural events (concerts, talks, debates). It has a number of gaming areas. And an Indiana university economics professor has been awarded a $240,000 MacArthur Foundation grant to develop and study a Shakespeare-themed area in the world. The Reuters news service has opened up an SL bureau documenting business, technical and cultural developments within the world.

Two million people do this?!

That's what Linden Lab says, though as of early 2007 journalists, such as Clay Shirky, were giving that number increased scrutiny. According to Linden's own information, as of last week, there were 2,371,468 uniquely named avatars with the right to log into the system, trade currency and so forth. More than a third, or 844,310, had logged in within the last 60 days, and 225,954 had logged within the last seven days.