Reaction: Now, because I use Spotify quite frequently, I knew that they make a compilation of all the music that you have listened to the past year and make a banner showing that you what you listened to and make that list into playlist for you and you are able to share this banner with people.
The Goal: By offering the users a fun and insightful data visualization to share, Spotify basically created a successful ad campaign and let their users do the work of promoting it. That kind of social proof is hard to beat. The Spotify Wrapped format is so recognizable, it even become a meme.