I'm obviously not a lawyer or anything but I think that this would be more compeling if Spotify was open source. "You don't want to share this? Well just remove the code then."

Here not only can't I do that but I've been a paying customer of Spotify for years and I had no idea that they even collected 90% of that stuff. In these conditions how can it be argued that I gave them ownership of data I didn't even know existed?