I notice that a lot of computer and programming books are now licensed under various permutations of the creative commons license. Half of the books published by No Starch Press and Apress (at least the ones I looked at) seem to be available directly or indirectly under creative commons licensing.
What is the business model for creative commons books? Does it hurt sales? Does it help sales by creating more buzz around a book? Has the wide availability of pirated copies (and pirated PDFs) of traditionally copyrighted books affected the book publishing world, and does this help or hinder the creative commons licensing process? How does the advent of ebooks factor in?