Amazon has removed books several times from everyone's Kindle readers. One time it was a copyright issue and they were quiet about the other times. The link I was referring to is:
http://illinois.edu/blog/view/25/21326?ACTION=POST&displayOrder=desc&displayType=search&displaySearch=1984&displayColumn=created&displayCount=1And it says in their policy that they have the option to do so.
Oops, I didn't see that Ernest already posted about this. Sorry.