I've just begun reading a terrific brand new book (publication date February 2008!), Here Comes Everybody : The Power of Organizing without Organizations by Clay Shirky. It's about how people are spontaneously and organically forming all sorts of groups and achieving all sorts of tasks via new electronic media.
He offers, for me, the clearest explanation of economic theory for how this works, and why we are at the beginning of a permanent, profound change in how people can relate to one another to act differently within, and upon, the world. (It's definitely clear, but a bit dense -- I had to reread portions a couple times.)
Example: after the London terrorist bombings, people on the scene uploaded a flood of photos (many from cell phones) immediately onto Flickr. These photos (and the people who submitted them) are linked together by common tags. Gathering this corpus of photos so quickly could not have been achieved by a formal "organization"; only a platform that facilitated lots of spontaneous, individual actions could enable it.
More to come.