The same question was raised by our friends over at jkOnTheRun.
I view scanning the book into a digital form for easier access to be firmly in the "fair use" camp. It is no different than copying or handwriting a single chapter of the book to take to today's lecture to avoid carrying the 8 pound textbook. I don't think an argument can be made that this exceeds fair use. Even the evil RIAA doesn't go after legitimate consumers who make digital copies of music files they own, they go after people who distribute and download copyrighted material they do not own.
http://jkontherun.blogs.com/jkonther...ack_asks_.html