Will Richardson makes an interesting case for the use of eReaders ala Kindle over physical books. It's a compelling argument (be sure to read the comments), and I'm even more convinced that I want an iPad.
While there is a case to be made (and I and others have made it) that iPads in schools create a problem in that they are consumption based, let's face it: a large part of learning is STILL about consuming material, and that's not necessarily a bad thing. There is even some evidence (from a tweet by @dianadell) that the current emphasis on discovery-based learning may be misguided. As always with education, I think good teachers use a mixture of pedagogical methods.
Anyway, the ability to share textual annotations around, say, a reading of Gatsby could have a fairly profound impact on class dicussions and students' understanding of the text, allowing for greater nuance in interpretation. It would also make it easier to MODEL active reading--something that's very difficult for students.
It would be interesting to do a comparative study of two classes reading the same text, one with physical books, the other using Kindle and sharing notes. With everything else the same, would the Kindle students show a deeper understanding of the text?