Is all the music I stream to my Sonos system going through Sonos' servers?

In short, no.  This blog post is factually incorrect.  The author posted in another thread here and you can read our response to his initial comments.  I've provided some of the relevant details below:

To be clear, Sonos does not send all play requests through Sonos servers.  There are four servers of ours which act as intermediaries between Spotify, Amazon, SiriusXM, and Deezer.

What information Sonos does and does not collect can be found in our privacy policy.  You have the option to opt out of providing usage data to Sonos.  Note that Sonos explicitly does not collect information on what you play.  If you have any questions on this information, we'll be happy to answer them.

I recently had a conversation with someone about this same question. Can someone from Sonos expand on what is meant by intermediary? Does that imply that there are metadata servers that provision access and collect usage data but aren't actually serving up content? For which services is this done today? Thanks

This is the Privacy Policy (Above link is dead). http://www.sonos.com/en/legal/privacy.html

Thanks Stuart. It appears there is no option to unregister once information is provided. Wonder if registration is product-specific or applies to all products once opting in. It's a little vague. Would like to see Sonos allow management of this by the user.

Any service supplier will collect usage data. I imagine the likes of Deezer et al collect what you listen to and when so they can provide targeted content e.g. A flow based upon your favourites, and see if their capital commitment to providing services is cost effective. As well as more service parameters than you can imagine. They need to pay the artists.