As you might now The Pirate Bay and piracy have been huge in Sweden. Spotify have changed that when it comes to music. By making it _easier_ to listen to music via their application than via bittorrent/kazaa/napster/dc++ downloading, they're now the most used music player in Sweden. Just a few years ago the Pirate Bay top 100 list was full of music. Now there's two (2!) music albums on it, the rest is tv-series and movies.
If you look at it that way, that piracy is the competitor not cd sales, the music industry has a great opportunity in Spotify in the long run.