Right now most of non-neutral networks exist specially outside of the US in cellular networks. They allow Spotify or other media streaming services deliver content to the user without charging user's data plan. Most of the companies competing in media streaming space, specially those with paid subscribers are big enough to pay the ISP for the fast lane (Beats, Netflix, Rdio etc). One exception is the fast lane (or maybe VIP lane in this case) for Facebook in developing countries. I've seen Facebook let users with no data plan whatsoever use the service in Türkie. You can see how this makes it hard for other social networks to catch up.

I don't think US cable companies make a tier system for websites. It doesn't make sense. All the non-media traffic isn't much that worth the discrimination. Most of the un-neutrality will be in cellular networks and media delivery.