Yesterday Facebook transformed itself into music and media discovery, listening and sharing powerhouse.  Via its API, Faccebook welcomed some of music's hottest startups: Spotify, Rdio, Soundcloud and more than a dozen more onto its pages. More will follow soon. But one major player is missing: Apple.

For most music fans - particularly the casual ones - Apple provides both the music store and the music plyer of choice. It's not a surprise that Apple is not on board. Without full iTunes integration,  music discovery will turn into far fewer purchases. 

Yes, some of the integrated services have iTunes purchase options. But any extra layer adds friction and extra friction means fewer sales.