In my opinion, this is one of the better stories on the future of the internet, not just Second Life. It covers today's virtual spaces, but also take an interesting look at what could be. Coincidentally, Google is buying the refreshments at the Serious Second Life Meetup on Thursday.
I think this transition will be in the consumer space in around 5 to 7 years. Right now I see it in the innovator's adoption cycle... crossing over to early adopters. If you want in on what will be, start poking around at this stuff now.
This story is an in-depth, 11 page read from Technology Review. Very well worth it. "Second Earth, The World Wide Web will soon be absorbed into the World Wide Sim: an environment combining elements of Second Life and Google Earth."
"You are here? In this imaginary composite, the virtual world of Second Life--as embodied in the author's avatar--meets the real world of Google Earth. Credit: Technology Review"
Nic over at Kzero has put together a pretty neat slide show of the major brands in Second Life. Remember though, I think everything happening right now in this world needs to be treated as experimental. If you're looking for profit, you're 5 to 7 years early.
This space has no analogue, especially to the current 2D web, so stats that work there do not apply. Building the 3D web will be fun, and these brands are helping it along. They get to have input.
Check it out: The definitive guide to brands in Second Life