There’s not much I can suggest to improve the Amazon.com business model. Today’s invention is, nonetheless, a small potential enhancement. Buyers of books or DVDs would be offered the chance to upload a hand-drawn picture or a handwritten message, imaged using eg a camera or cameraphone.
This would be printed onto some spare space on the existing paperwork included in the delivery packages (possibly with a self-adhesive strip around the outside). This would be inserted in the postal box at the dispatch warehouse so that a recipient could then stick the personalised dedication into the book or DVD case.
(For people who can’t draw or spell or have limited expressive ability, there could even be a selection of standard templates provided online in sufficient numbers of combinations to offer a measure of genuine personalisation).