Shirky begins with a premise about human nature: we're social animals and like to form groups. Recent changes have radically reduced the costs of doing so, broadening access to "capabilities [e.g. publishing] previously reserved for professionals" (p.17) and thus empowering people to organize themselves, with occasionally spectacular results. Shirky writes (p.22):
The current change, in one sentence, is this: most of the barriers to group action have collapsed, and without those barriers, we are free to explore new ways of gathering together and getting things done.
The fuller explanation involves Coasean economics. (1) Note that transaction costs would skyrocket if everyone worked freelance, constantly negotiating in the marketplace. That's why we have firms ("organizations"): it can be more efficient to have managers simply order their employees about. (2) However, managerial overhead brings its own costs. This implies what Shirky calls a Coasean floor, beneath which lie potentially valuable activities that cannot be profitably realized by either market or institutional means. However (p.47):
Now that it is possible to achieve large-scale co-ordination at low cost, a third category has emerged: serious, complex work, taken on without institutional direction. Loosely coordinated groups can now achieve things that were previously out of reach for any other organizational structure, because they lay under the Coasean floor.
The cost of all kinds of group activity--sharing, cooperation, and collective action--have fallen so far so fast that activities previously hidden beneath the floor are now coming to light. We didn't notice how many things were under that floor because, prior to the current era, the alternative to institutional action was usually no action. Social tools provide a third alternative: action by loosely structured groups, operating without managerial direction and outside the profit motive.
It's a nice enough analysis, but the real value of this book lies in its illustrative examples. Shirky discusses everything from Flickr, blogs, and open source software, to flash mobs, political protesters, Wiccan meetups, and Catholic lay groups self-organizing for the first time ever to reform the Church.
There are also little insights scattered throughout the book. Consider, for example, the common disdain felt towards the "drivel" posted on Livejournal and the like (pp.85-6):
We misread these seemingly inane posts because we're so unused to seeing written material in public that isn't intended for us... if you were listening in on their conversation at the mall, as opposed to reading their post, it would be clear that you were the weird one...
Most user-generated content isn't "content" at all, in the sense of being created for general consumption, any more than a phone call between you and a relative is "family-generated content." Most of what gets created on any given day is just the ordinary stuff of life--gossip, little updates, thinking out loud--but now it's done in the same medium as professionally produced material.
I also liked his point about the impossibility of full-blown interactivity with the famous, no matter what technology we might come up with. To be famous is to receive more incoming attention than one could realistically hope to reciprocate (by any means). So even bloggers, when they hit the big time, are forced to become mere broadcasters rather than responsive participants in an open conversation. (A good reason not to desire fame, I should think!)
The book also contains some interesting thoughts on political and social change, especially the importance of "lower[ing] the hurdles to doing something in the first place, so that people who cared a little could participate a little, while being effective in aggregate." (pp.181-2):
Having a handful of highly motivated people and a mass of barely motivated ones used to be a recipe for frustration. The people who were on fire wondered why the general population didn't care more, and the general population wondered why those obsessed people didn't just shut up. Now the highly motivated people can create a context more easily in which the barely motivated people can be effective without having to become activists themselves.
One thing Shirky emphasizes throughout is the way that so-called "cyberspace" is growing increasingly intertwined with meatspace. He discusses using his mobile phone, and a service called 'dodgeball', to learn that a friend of a friend was currently in the same NYC bar. Conversation ensued: "I'm Clay. If Dennis were here, he'd introduce us." (p.219) Pretty amazing, really, and something we can expect to become increasingly common.
Finally, a couple of cute philosophy quotes:
The groups now adopting social tools form the experimental wing of political philosophy, a place where hard questions of group governance are being worked out. [p.? lost it.]
Wikis take on one of the most basic questions of political philosophy: Who will guard the guardians? Their answer is, everyone. [p.272]
Note that if you're looking for a rigorous academic work on social media and the promise of peer-production, you can't go past Yochai Benkler's Wealth of Networks (available for free, here). But Here Comes Everybody offers an accessible introduction to the broad issues raised by social media, so I would especially recommend it to non-specialists who are curious to learn what all the fuss is about.