Imagine your best friend, Rachel is getting married but having a hard time choosing songs for her reception. Weddings are a very intimate affair, and unlike Spotify's suggested playlists, requires a more careful curation – the factors for which largely depend on the event theme, cultural context etc. This feature would help Rachel curate a playlist based on her friends' recommendations for the wedding.
Rachel can create a blank playlist, set the duration for her event, add theme details (dance, hip hop, pop etc.) and ask for suggestions; or alternatively, add a bunch of tracks and seek votes from her friends. The higher the number of votes, the greater the popularity. The social poll feature can be made available within Spotify's app and can be integrated with other channels like Instagram Stories and Facebook.
The idea is primarily applicable for wedding receptions but can be extrapolated for other events as well (themed parties etc.). I would love to hear your thoughts.