You learn something every day.
What I learnt was that the reason my internet connection was getting hammered was because the downloadable spotify app that you can install on your computer actual transforms your computer into a P2P network.
If you have the software installed then you can do a search and block spotify's ports and stop the band leaking.
If you use their web player then this will not happen, so you can just switch to that. Or if you're just looking for endless streams you could download the DI player and avoid all this spotify stuff. Or if you live in a country that doesn't respect the Berne convention then this would be the app to install and build you own library.
But I do find it quite cheeky that they are munching the upstream of it's users, and that this will even extend to people that are paying for their music delivery service.
Of course if they told peple they were running it as a P2P perhaps they would have been equated to naptster and that wouldn't have wrapped well with the launch would it. But this is the wild wide web.