An idea I just had was that Spotify should add a collaboration section. So when you have a bunch of people you are with they can all collaborate on the playlist that is playing through the application. For example, if everyone was connected to the same network, the app would pick up on that and generate a playlist that everyone with the Spotify app could add to. This could potentially add to the users of the application, because if the group is playing music through the application one would want to be included and then download it. The playlist could stay active for 24 hours so the collaborators can choose whether to follow it or not. This would generate great memories for friends while also promoting the brand and generating revenue.
Hello! This is already possible: On the desktop version right-click on a playlist => Choose 'Collaborative Playlist' and share the playlist link with all the people that you would like to have them songs added. Enjoy! ;)