How Spotify streaming works:
http://pansentient.com/2011/04/spotify-technology-some-stats-and-how-spotify-works/
- Spotify is the only on-demand music streaming service that’s not web-based. Instead, it uses a peer-to-peer network (p2p) that can scale up to meet the demands of millions of users.
- Only 8.8% of music playback comes from Spotify’s servers. The rest comes from the peer-to-peer network (35.8%) or your local cache (55.4%). The exception here is Spotify on smartphones, which gets all the music directly from the Spotify servers.