This would be great, but imagine how much data would be used in order to stream music to the car. Tesla's 3G bill would run them out of business, unless they turned the cost over to us.
I had a Tesla rep mention to me that the current Tesla agreement with Slacker in North America ends in the summer of this year, and to his knowledge the agreement still has not been renewed. I hope that the success of Spotify in other countries would lead them to really consider leaving Slacker for Spotify in the US