Actually a transcript of a speech by Clay Shirky, this might be useful input for some students. The concept of cognitive surplus is fascinating. In this excerpt an interviewer was asking Shirky about Wikipedia and how users actually write the articles themselves:

I think, “Okay, we’re going to have a conversation about authority or social construction or whatever.” That wasn’t her question. She heard this story and she shook her head and said, “Where do people find the time?” That was her question. And I just kind of snapped. And I said, “No one who works in TV gets to ask that question. You know where the time comes from. It comes from the cognitive surplus you’ve been masking for 50 years.”

So how big is that surplus? So if you take Wikipedia as a kind of unit, all of Wikipedia, the whole project–every page, every edit, every talk page, every line of code, in every language that Wikipedia exists in–that represents something like the cumulation of 100 million hours of human thought. I worked this out with Martin Wattenberg at IBM; it’s a back-of-the-envelope calculation, but it’s the right order of magnitude, about 100 million hours of thought.

And television watching? Two hundred billion hours, in the U.S. alone, every year. Put another way, now that we have a unit, that’s 2,000 Wikipedia projects a year spent watching television. Or put still another way, in the U.S., we spend 100 million hours every weekend, just watching the ads. This is a pretty big surplus. People asking, “Where do they find the time?” when they’re looking at things like Wikipedia don’t understand how tiny that entire project is, as a carve-out of this asset that’s finally being dragged into what Tim calls an architecture of participation.

I also highly recommend Shirky’s new book Here Comes Everybody.