So the other thing with the Tracking Protection experiment is that we're soliciting feedback about how this feature breaks the web. We use a block list from Disconnect for Tracking Protection in Private Browsing and for Focus on iOS, but until now had very little understanding of how enabling this feature might affect browsing.

For the Test Pilot experiment we're asking users to tell us where and how the feature messes up websites so we can refine our Block list and improve the experience for everyone. We're already getting a lot of significant data and intend to share it soon.

How about removing referral headers, report back very common user-agents, accept headers, language headers, screen resolution, etc. Take a look at https://panopticlick.eff.org/

Does anybody know if a extension/browser etc. exists that can spoof the common JS features that make users identifyable?

Its basically adblock-lite. Prevents HTTP requests to domains that are known to be used for tracking.

Well, each and every page/widget/JS script belonging to Google/Facebook/Microsoft/Twitter/etc. are known to be used for tracking.