I didn't understand that point completely from the article though. Spotify lets you look at what other users listen to and their playlists (if they haven chosen to show them to the public) and I can subscribe to those playlist as well. The thing I guess they talk about is that you can't see who listens to a specific artist, you won't be able to get a huge list of usernames that listen to a certain artist. I guess they keep those goodies for themselves ;)