The digital music is a tough business. Many very interesting ideas have been tried and not all of them really succeeded. This a collection of their stories, for reference.
Microsoft Zune/Xbox/Groove Music
Apple: Ping, Connect, itunes DJ, Beats
Rdio
Twitter Music
Last.Fm
Turntable.fm
Songza
Google Play Music
Deezer
Soundcloud
Tidal
This is my jam
8tracks
Some tangential content, but very good readings.
