It's tough to create a playlist that your friend or partner will enjoy just as much as you do, especially if your tastes don't quite sync up. How are you going to reconcile your fondness for tender folk music with your pal's addiction to drum-and-bass? Spotify thinks it has an answer. Its Mixmates website crafts playlists based on both your favorite artist and that of your buddy, creating Kevin Bacon-like degrees of separation from song to song. If you like the resulting mishmash, you can save the playlist for posterity.