Don't like being tracked and having ads that are supposedly pointed towards you popping up? Both Mozilla and Google are implementing new ways to "opt out" of these types of ad tracking in updates to their browsers.
Google is using a cookie based approach for Chrome, calling it "Keep my Opt Outs." This extension is explained as being able to "permanently [opt] your browser out of online ad personalization via cookies." The big bonus here is that it will work well with Google based ads, which tons of sites use so it will be more noticeable in most user browsing sessions.
Mozilla's plan for its Firefox browser includes an HTTP header that tells web sites that the users wants to opt-out of OBA. Alex Fowler, Mozilla's global privacy and public policy leader, stated that they "believe the header-based approach has the potential to be better for the web in the long run because it is a clearer and more universal opt-out mechanism than cookies or blacklists." This is different from other cookie or registry opt out functions.