During a discussion with someone else about giving things away that you'd normally charge for, this insight came up: When you take the price tag off something, you deprive most people of the easiest way they have to gauge its value.
I meet a lot of folks at cons who aren't rich, but they've often doing okay and are at the con because they can spend a little something for themselves. Or they may be folks who don't have money to spend right then, but spend money in general. In both cases they see that $12 + sales tax for a paperback book is a good deal, especially when many other people in the same space are charging $25 and up for same. (News flash to self-published authors: you need to achieve price parity with mainstream publishers, not other indie authors, because you're competing with all of them too.)
There are a few things I give away, but they're adjuncts, not the main product. Every book has a PDF sampler, and I sell paper copies of those at the conventions with the price of the sampler applicable towards a discount on the full book. The main event, though, will always have a pricetag on it — because that gives people a commonly-understood way to budget their degree of involvement with it.
If I took that away and started simply giving out copies of the book online, I'd be doing myself more harm than good. The fact that I'm willing to charge a price for what I do is a message that I think it's worth something, that I think it's going to be that much more developed and substantial and noteworthy than something just slapped up onto a webpage. Henry Rollins once talked about his publishing company 2.13.61 like this: "I am just pretentious enough to assume someone will want to read what I wrote." Just pretentious enough to package it up, print it, charge money for it. He seems to be right about that: his books sell well enough that he can keep bringing them out quite reliably.
I'm not trying to denigrate people who, for instance, have their own webcomic. The model there is to give away most of the content up front. But a lot of those folks anthologize their work and sell it in print form, which means on some level they think it's worth paying for. Apparently they do pretty well with such things, because — surprise! — people feel those things are more than worth paying for.
I myself am still flirting with the idea of developing a serially-published story that will be initially given away, but eventually turned into a kind of "donate this much to continue" project (with anthologies available later on as part of the donation process). But I want the story I have in mind to congeal that much more before I attempt it. And I plan to sell it in its completed form — whether that comes to 200 pages, 500, or what have you.
I like the idea of the Creative Commons, and I know I've made use of material licensed as such in the past (the cover for Tokyo Inferno was taken from a CC-BY photo). But I think it's an adjunct to existing systems and not a replacement for them — not unless you plan to do away with money. And look how well that's worked out in the past.