I think Spotify getting this feature working wouldn't be trivial as syncing audio perfectly across different Internet devices (labtop, PC, tablet, phone, etc) doesn't seem doable. Also, music licensing issues would probably be an issue too.
Adultfriendfinder is one of the largest sites on the net. People love to get off and be watched and vice versa. Also male bonding of circle jerks has been around forever, which is taboo, but obviously millions share this desire.
For another site that may shock or thrill you check out cam4.com . People showing their face all ... don't these people have a career/job/friends/family? WoW
I think Spotify getting this feature working wouldn't be trivial as syncing audio perfectly across different Internet devices (labtop, PC, tablet, phone, etc) doesn't seem doable. Also, music licensing issues would probably be an issue too.