I do think the petition has a good point beyond the deletions. Personally, I agree with them that Amazon isn't quite clear enough about the limitations of the DRM. IMO all companies that sell DRMed content should have an explicit list of what you can and cannot do for your money. It should be up front, detailed, and easy to understand.
For example, take the whole kerfuffle about people running out of licenses that happened a few months ago. Amazon tells you quite clearly on the product page that you can read your books on "up to six" Kindles. That's not a lie, but it's not exactly a detailed description of the real limitations and quite a few people misunderstood how the system worked. The reality is that most books do indeed allow six licenses but the user doesn't have a way to transfer the license. It is tied to the Kindle, not the account. People didn't understand that when they deregistered a device, the license wasn't freed up. Amazon also doesn't tell you how many licenses a specific title allows. If it's fewer than six, that should be clear on the product page along with the warning if TTS is disabled. I've had a Kindle for almost two years and it just became clear a few months ago how the licenses worked. That's not playing fair. I understand the drive to keep marketing literature concise and to highlight the positives but I think it serves both the customers and the business to be transparent. They could have saved themselves a lot of bad PR.