A patent filed by Apple is suggesting that the next iPhone would include Near Field Communication. The patent, published by the US Patent & Trademark Office on April 26 suggests that it talks about transferring digital media content from one user's account to another.
At current, NFC isn't available on any Apple product. But if it were it would allow you to make a transfer by tapping devices together. Or bumping them if you prefer. Purchases could also be transferred via email.
In addition to sending individual tracks, the patent suggests that Apple will allow users you share playlists with others -– like a modern day version of the mix tape.