I value ebooks less than I otherwise would because the DRM makes them scarily impermanent. I have no faith at all that, five years from now, the ebook I buy today will still be readable. You might think I could replace my reader even if it died, but what if the reader's entire product line dies out? (That's not exactly a thought experiment: Every reader prior to the Kindle died out; the Newton died out; even very successful platforms like the Palm died out.) What if the software becomes extinct? What if the publisher goes bottom-up?

And given that the net cost of buying the book used, reading it, and then selling it used is so small (or even smaller, if it's the kind of book one can find at the library) it's hard to justify the ebook. Frankly, if it wasn't for the superior physical experience of carrying, handling, and storing an ebook nobody would bother with the things. Even the crappiest trade paperback I own has an order of magnitude longer shelf life than any DRM system.