Cleverboy, aka Dudley, is just that kind of iPhone hacking genius, he is the same guy who had figured out how to add ringtones using iTunes by just changing the extension. He has now figured out what differentiates a song from a ringtone as far as iTunes is concerned.
Cleverboy was the one who had posted instructions on how to "convert" AAC music files to ringtones in iTunes 7.4. (see iPhoneHacks.com, Add Custom Ringtones to your iPhone with iTunes 7.4 for FREE. Seriously?) Apple had to come up with an emergency release to fix the bug in iTunes. That seems to have motivated the iPhone hacking genius to dig deep into the m4a metadata to figure out what identifies the role of a file.