We have heard of buying and selling of used books but not of re-selling e-books.
Since now e-books sell more than the books, selling and re-selling of e-books should become a norm rather than exception in ear future.
To begin with reselling of e-books, Amazon has obtained a patent Jan. 29 that covers a marketplace for moving digital books, audio files, video files, apps and more from one device to another. Once the new device receives the "used" e-book, podcast or other digital object, the file gets deleted from the original device.
Amazon may not immediately open up such a marketplace. Companies regularly file for patents they don't plan to use soon, or ever. The new patent does bring up interesting questions about whether reselling digital files is legal, and who may broker such resales in the future.