I follow artists to keep up with new releases, and individual users with dope taste.
It's awesome that "Activity" is finally on mobile, but Spotify needs to better encourage social activity. I think a "badge" system would seriously incentivise following, sharing and seeking out other people's playlists (I've got thousands of followers yet still feel anonymous :/humblebrag)
I really enjoy the "following" aspect of the Spotify community, but it could be improved upon. I'm not suggestion that Spotify emulate Facebook in any fashion, but I would propose that the profiles of Spotify users were more accessible. I use Spotify to send music to people on a regular basis and also to discover music that my professors and friends listen to. As an active musician and music student, this is very useful, but could be improved. The ticker on the right side of the desktop app is nice, but should be expanded or optimized for more of a musical community.