One of the barriers to adoption of the Amazon Kindle is its price. One of the things that makes it seem expensive is surely the price of books. For example, I usually buy paperbacks at $10 or less, so >$300 seems huge. But the Kindle might be particularly attractive to people who spend a lot on books.
College students certainly spend a lot of books. Textbooks for a single semester often cost more than a Kindle. Hence I think that Mike Arrington and others are right on the money when they identify college students as natural Kindle users.
The trouble is, college students don’t have much choice when it comes to textbooks. The professor usually chooses the textbook for the course from what the publishing firms offer. The incentives to the prof and the firms don’t always align with the best interests of the students.