This article (PDF), written by one of the folks at Linden Labs, pretty much summarizes the philosophy that led to the development of Second Life.

I tend to agree, especially on the difference between MMO-style “crafting” and actual creation, and the fact that the latter is vitally necessary for any virtual reality system to truly succeed.

As an example, behold my first vehicle (It really flies, though I didn't write the scripting for that. I will eventually replace the existing script with my own, because a Recognizer is not really an airplane, and landing one that pretends to be an airplane is sort of painful ^_^)

Also, there was recently a spot on Fox News about SL, which you can watch online here (direct link) or here (see the thumbnail on the right sidebar).