My understanding is that Firefox, and eventually all the other browsers, intend to do something like this by default. They are all working to prevent cross site tracking, linking your activity on one site to your activity on another. For example, Chrome has: "In parallel to that we will aggressively combat the current techniques for non-cookie based cross-site tracking, such as fingerprinting, cache inspection, link decoration, network tracking and Personally Identifying Information (PII) joins." -- https://www.chromium.org/Home/chromium-privacy/privacy-sandb...