I love that Spotify automatically adds songs that I give the thumbs up to on a radio station, but like most people, I listen to lots of genres that are somewhat "mood based." For instance, I don't want to pull up that playlist (liked from radio) only to hear Drake, followed by Dave Matthews Band, followed by Gym Class Heros.
When my iTunes playlists were imported, it created a hierarchy / parent / tree structure (not sure how to describe that in a technical way!) so it seems like the technology is already in the app, just not being used on this feature. It would be hugely helpful and hopefully easy to implement.
Thanks for the consideration!

end-user should be able to create TAGS for songs. include standard tags like "rock" and "soul", but allow the user to create their own tags, and use this as cross-referenced information to organize not only the user's own music collection, but also to match characteristics of other users' music or playlists. user-created tags would allow Spotify to recommend more musically accurate songs, as the characteristics and style of the songs have been peer-reviewed. it's no secret that Spotify radio is weak. Utilize the social network of Spotify by tapping into the users' knowledge and experience of music.