Bump is an older app on the App Store that allowed you to "share" contact information with another local phone not actually by Bluetooth, but by simply placing the two phones near the same location, and then sharing the information across a wireless network. Now, Bump is apparently adding a new trick to its arsenal. In version 2.2, out on the App Store now, you can actually "share" any of the songs in your iTunes library. Bump still doesn't actually push information from phone to phone -- instead, it will read out the song's information, and then give the receiving phone a YouTube link to hear the song, as well as links to preview and buy the song on iTunes (assuming it is available).
It's an interesting way of getting around the licensing restrictions that have prevented hearing the same music on multiple devices, and of course it solves the trouble of getting two phones up and wirelessly connected long enough to actually push a file across. A neat little bit of innovation for an app we installed on the iPhone a long time ago.