First Mozilla detailed its "do not track" system for Firefox, and now Google has announced its own version for Chrome. Keep My Opt-Outs is a Chrome browser extension that takes advantage of ad industry regulations around personalized web adverts; basically, it lets surfers permanently opt out of ad tracking.
"Keep in mind that once you install the Keep My Opt-Outs extension, your experience of online ads may change: You may see the same ads repeatedly on particular websites, or see ads that are less relevant to you." Google
Now, as with the Firefox system, this relies on the ads being served by one of the 50+ companies which support the opt-out program - there's no way to blacklist other ad servers, for instance. Google plans to develop versions for other browsers, and the Keep My Opt-Outs code is open-source.