Amazon has a patent to sell used ebooks. When I first scanned the headline, I thought it must be some Onion-esque gag, and I'm sure I wasn't alone. Used e-books? As in, rumpled up, dog-eared pdfs? Faded black-and-white kindle cover art, Calibri notes typed in the margins that you can't erase?
Barely-amusing image aside, used ebooks are for real. Or at least have a very real potential to become real. See, Amazon just cleared a patent for technology that would allow it to create an online marketplace for used ebooks--essentially, if you own an ebook, you would theoretically be able to put it up for sale on a secondary market.