I think it would be great to go to an artists page, and be able to see which friends listen to that artist. Right under the "followers" indicator could be a "friends listening to this artist" indicator, and clicking on it would show which friends have played songs by that artist the last month (or have added songs by that artist to their playlists).
Updated on 2018-03-12
We’re here to let you know we've retired the feature showing your which of your friends listen to an artist on our Artist Profiles.
Of course, we always take retiring features in Spotify very seriously. We'll continue putting energy into new ways of sharing music discoveries with your friends on Spotify.
Please post here with any questions or feedback you might have. We’ll be sure it reaches the right teams.