Make social integration smoother.
Spotify has a high profile relationship with Facebook, and it'd be great if they took more notes from them when it comes to social media. The social functions contained within Spotify should be more developed. Sometimes we don't want Facebook friends to know what we're listening to, and we don't feel like sharing out playlists with our Twitter timeline, but until Spotify's native social components are updated, that's all we have.
If the social functionality of Spotify was focused on the app itself, then the average user would be much more apt to embracing it, knowing that their listening habits are only being shared with and judged by a like minded Spotify-using community. Plus, it's simply more practical. If the Spotify discussion is mostly happening on Spotify, it's a win for users and the service.