I'm a little conflicted about this. The Echo Nest is <i>amazing</i> and does the kinds of things with music analysis that I can only dream of doing, so I wish them every success in the world.<p><i>But</i> up until now they've been a fantastic independent force, not attaching themselves to any single music provider. You could use their APIs with Rdio, GrooveShark, whatever you felt like. I'm concerned that will no longer be the case.