In pulling from its virtual bookshelf the disgusting The Pedophile's Guide To Love & Pleasure: A Child-Lover's Code of Conduct, Amazon proved that even the largest retailer is not immune to public pressure, and that community standards - however fragmented or ill-defined - still carry weight in the marketplace.
The only surprises in this situation are that (1) Amazon decided to sell the book to begin with, and (2) that it tried to support that decision with a "freedom of speech" argument. In this case, the right to freedom of speech should be strongly trumped by the basic tenets of human decency, the violation of which threatens the foundation of our society. If that sounds overly dramatic, then you're just not paying attention.
One of the first websites to break this story was TechCrunch, and this article focused on an interesting phenomenon: the apparent reliance on "the Red States" and "Middle America" to be the moral gatekeepers for America. I suspect the public outcry against this book was more widespread than that, and I would caution any one group from thinking it has a monopoly on the moral high ground in general, but to the extent that "Red State" residents succeeded in convincing Amazon to change its corporate mind, I proudly claim citizenship in that group.