mark suster wrote a good post on this: http://www.bothsidesofthetable.com/2012/04/14/dont-try-to-pu...

You could combine priceonomics data + taskrabbit work force to scale the arbitrage business on high value items. ;)

Seems like Facebook might've asked for this as part of the integration deal. Otherwise I see no obvious reason for Spotify to limit their customer base. Unless the economics of delivering music to a non-facebook user is much less attractive and have much lower conversion to paying user? I find music discovery on Spotify to be poor compared to Pandora, and without my FB connections sharing playlists, I have no incentive to pay for Spotify.