The issue I'm taking with this is that Spotify did not try to hide, be cagey or act deceptively about the p2p aspect of their design at all; in fact here is a 2011 article on an academic paper on the design
http://pansentient.com/2011/04/spotify-technology-some-stats... and here is a question-and-answer from their support community about it, from 2013:
https://community.spotify.com/t5/Desktop-Linux-Windows-Web-P... Hardly a design aspect that everyone who actually cared about such things was intentionally kept in the dark about.
I would feel it is justified to be miffed if they tried to do it in secret and it was determined that they did indeed try to hide or downplay this fact, but this is not in fact what happened. Their stance seemed to be "yeah, this is currently how it works, we know some customers are unhappy with the arrangement, so we'll eventually change it, but you can't currently turn uploads off." Thus, you are basing your indignation off your own ignorance, and not reality.
Full disclosure: Am long-time Spotify fan (hey, gotta be honest!)