Buried in the fine print of those "terms and conditions of use" is a forced arbitration clause. That means that if you have a dispute with Spotify, you have to take your case to a decision maker at a firm they choose -- not a judge or jury. In addition, if Spotify violates the rights of thousands, even millions, of its listeners, they can't band together to seek justice.
It's been a few years now since I began paying for Spotify's premium service, and to my enormous surprise I think I've been converted. Sure, I still buy some CDs and download albums that I think I'll want in my "permanent" collection. But most of my listening these days has been on Spotify. And, I've begun to understand why.