What if someone made a browser plugin where every time an you visited a website it gave that website 1/1000th of a cent (and took 1/1000th of a cent out of your paypal/google-checkout/etc. account), and in exchange that website saw the plugin and served you a version with no ads. How many people would choose to use this plugin?
You don't have to get every website to support it, just the big name advertisers. If the money went straight to adwords... that covers 80% of web real estate.