This is brilliant, not only for privacy but for speed. Seeing this makes me wonder why I didn't build this yet. I've often thought that Javascript loading tags could include a hash of the desired resource and your browser can fetch them once only for a thousand page loads on a thousand websites. This is not that, but it is extra local caching and on top of that it stops most tracking by CDNs. Guess I always thought of it as something my browser should have instead of an addon.