I'm unfamiliar with browser design. What parts of this need to be implemented by the ad networks, and what parts need to be done by the browser? I would have

I'm unfamiliar with browser design. What parts of this need to be implemented by the ad networks, and what parts need to be done by the browser? I would have thought that clearing your cookies goes a long way. Is it technically possible for a browser to activate a TOR service for a "Do Not Track" feature?