I use Spotify and had been recommending them to friends as well. I know several of my friends don't have Facebook, so this will probably stop them from signing up.

As far as automatic sharing goes, I've already told several of my friends that they can change their sharing to the "only me" setting so that they're not spamming what they're playing on Facebook.

I enjoy Spotify, but it is kind of a hassle to have to change settings to make it usable.