This video from TED Talks is worthwhile for those wanting to better understand Second Life and virtual worlds. I'm linking to it rather than embedding it here because the comments on the TED Talks page are worth reading.
Rosedale makes some strong statements at the end of the video on how he believes that virtual worlds are the future of the Internet. That's still difficult for most of us to imagine. Research reports projecting significant growth in virtual worlds over the next few years have been published by Strategy Analytics and Gartner . This blog post "The Future of Internet Is Virtual Worlds. Or Is It?" takes an opposing viewpoint.
I personally don't know whether virtual worlds will be the future of the Internet. Seems it would be awfully difficult to predict with how quickly technology is developing/changing. But I do believe virtual worlds will have an important part in the future of education. Those in higher education can take a look at my post on the Sept/Oct 2008 issue of Educause on virtual worlds.