Came here to say this. My guess is that Amazon paid them to go away. If my guess is accurate ( I could certainly be wrong ), then Amazon could have them add a robots.txt banning archive.org. If they do that access to the archive will be removed. Mirror it now if you want the content.
One nice way to do so ( handy for any site that you think may vanish off Way Back Machine ): https://github.com/hartator/wayback-machine-downloader