I am confused with this whole thing as well. I thought it just gave me a way to listen to my music on my iPhone without transferring it to the phone. Now that I am running this sync, I think I am actually transferring this entire playlist from my laptop to my phone. I DO NOT want to do this and now I don't know how to stop it and get all this crap off my phone! This whole playlist is not going to fit on my phone so it will completely fill my phone up, which will cause problems and sluggishness with my phone now. I am not a happy camper!
Also, something else that I might should have researched a little better before doing it but if I have installed the Spotify app on my MacBook, when I link to friends accounts and synch or whatever it is called with my iTunes on my laptop, am I putting another copy of the music on my computer? If that is what is happening here, again, I am not a happy camper and I now need to know how to make all these superfluous files go away without leaving traces on my new MacBook Pro! I have been so careful about what I have installed on this computer, trying not to install a lot of apps that I will never use and even deleting some things that I don't us so as to not take up the space. Now I am worried that I have defeated my efforts by signing up for this stupid music service without completely understanding what I as doing. Of course, it's my own dumb fault for not reading everything thoroughly before doing it but I've been reading so much about all the advantages that I neglected to consider the disadvantages!