I think you're putting too much faith in blocking third party cookies. Through collusion with Google (such as an IFRAME or JSONP), sites can get your Google ID

I think you're putting too much faith in blocking third party cookies. Through collusion with Google (such as an IFRAME or JSONP), sites can get your Google ID from your Google cookie without needing to consult your IP address or use third party cookies. Web browsers open up such a huge can of privacy worms that I don't think it's very useful to talk about IP addresses until you fix the browser. Personally, I clear all cookies, cache, and local storage (except from a handful of trusted sites, Google not being one) when I exit my browser (and I exit my browser often), and I occasionally examine my browser profile for traces of super-cookies. (And even this is probably not sufficient because of browser fingerprinting.) I don't think privacy extensions provide an appreciable privacy improvement over stable privacy addresses.