So, the story of what happened with AmazonFail is in, and it was, indeed, a glitch of sorts. There was no massive conspiracy to exclude certain works from rankings and searches. In fact, it seems the issue had to more with language barriers -- and an unfortunate lack of quality control administration -- than anything else.
It seems someone editing the code for Amazon.fr (Amazon's French portal) conflated the word "adult" with the word "sexuality." All of Amazon's portals everywhere are linked, so the local change in France propagated throughout ALL of Amazon.
I can only imagine the PR nightmare this all has been to Amazon. Amazon says it will take some time to repair this issue. I kind of feel horrible for the guy who made this mistake. Once the torches and pitchforks were headed hsi way, his blood must have run cold... But it's not really his fault. This is a great lesson on why multiple levels of quality control are a fine idea. Think of the damage this person could have done if they were trying to be malicious.
SeattlePI has the whole story.