On October 5th, Google sent several subpoenas out to companies like Microsoft, Yahoo and Amazon who have book scanning projects similar to Google Books. Amazon.com said no to the request for information about the workings of their book scanning efforts almost immediately, and Yahoo just today followed suit by declining. Yahoo says the request is "a brazen attempt to pry into its trade secrets".
I would be very surprised to see any company give trade secrets to a direct competitor -- but I guess it never hurts to ask? For more information on this story, check out this article by David Utter of Web Pro News.