"when Spotify wasn’t playing audio, it was using my network connection. A lot."
"not immediately disclosed by Spotify: the application employs built-in peer-to-peer networking technology to share streaming music from its cache on my computer with other Spotify users who want the same tunes, presumably taking the load off Spotify’s own servers. There’s almost no mention of this P2P functionality on Spotify’s own site. And no way to throttle or turn off the upstream P2P use in either the free or paid version which, probably, is a key part of Spotify’s business and technology model. "
http://www.geekwire.com/2011/practical-nerd-hidden-price-free
