While not many people (myself included) believe that this book belongs anywhere, it does raise an interesting question. Initially, Amazon claimed it did not censor its self-published offerings; later, Amazon confirmed the title had been removed but refused to comment on the matter.
For my opinion on the matter — and to share your own — keep reading.
I'm for free speech and the right to self-publish a book, even though I certainly don't support the book in question. I'm not sure I believe it's Amazon's job to police every single title available on its site. It almost seems like a double standard — everyone complains when a site (Apple's iTunes Store, for example) starts imposing rigid rules on people who submit their creative works (in this case, apps), yet when an online retailer allows somewhat open submissions, people are bound to find something offensive.
In this case, the book promoted illegal activity and clearly shouldn't have made it onto the site. But are other titles that may push boundaries or toe the line Amazon's responsibility to monitor? The author's responsibility? Or does it fall on the consumer to distinguish what he or she believes is acceptable?