"Imagine treating the free time of the world's educated citizenry as an aggregate, a kind of cognitive surplus. How big would that surplus be? To figure it out, we need a unit of measurement, so lets start with Wikipedia. Suppose we consider the total amount of time people have spent on it as a kind of unit - every edit made to every article, and every argument about those edits, for every language that Wikipedia exists in. That would represent something like one hundred million hours of human thought* ... One hundred million hours of cumulative thought is obviously a lot. How much is it though, compared to the amount of time we spend watching television?* Of his Wikipedia time estimate, Shirky says: "Martin Wattenberg, an IBM researcher who has spent time studying Wikipedia, helped me arrive at that figure. It's a back-of-the-envelope calculation, but its the right order of magnitude."
Americans watch roughly two hundred billion hours of TV every year."
That one comparison alone gives plenty of food for thought. Shirky's style is to carefully reinforce subtle points by repeating similar examples (often with similar paragraph structures) which can make the book seem repetitive. But he is repeating in order to tease out the subtleties; every example he gives in the book is saying 'people can work together to do stuff' - which is obvious - but the value in his examples is the deeper anaylsis of how they are working together, why, and how more of the same can be made to happen.
See also this Guardian Review
Near the end of the book, one paragraph in particular really stood out for me, not because it was about anything internetty, but because Shirky casually crystalised a thought that I had been struggling to form - about 21st century politics and how it is converging on variations of 'free market with state support for some things', with the 'big ideas' of the 19th and 20th Century now seeming hopelessly simplistic:
"Neither perfect individual freedom nor perfect social control is optimal (Ayn Rand and Vladimir Lenin both overshot the mark), so it falls to us to manage the tension between individual freedom and social value, a trade-off that follows the by-now-familiar pattern of having no solution, just different optimizations that create different kinds of value, and different kinds of problems that need to be managed."