Apple has patented a bundle of strategies to create and maintain a used/borrowed market for digital goods such as games, movies, books, and software.
Eurogamer reports on the patent, which implies users could sell or loan out purchased content to other users.
During an exchange, the store the piece of content was purchased from is notified. The store then checks whether one or more criteria are met, like price or the length of time since purchase, and then authorizes it for transfer.
In a re-sale, the content permanently moves from the seller to the buyer. The seller is no longer able to access the content. If loaned, ownership eventually returns to the user who made the original purchase.
Naturally, content creators have the potential to take a portion of the re-sale.
The patent also mentions selling only bits of content, such as game demos, portions of books, and movie extras.