Maybe it's time to limit browser to 2 levels of IFrame and 2 redirects in an IFrame... let the ad companies figure out how to pass/share their data directly instead of adding payload to the browser. It's entirely possible for the ad networks to proxy their requests instead of layers of IFrames, scripts and redirects.

The other side is that any advertising re-sellers should have to put up a bond/insurance against serving malware. If you get busted, you're out. It's up to the advertising companies to ensure that they don't deliver malware. If a campaign includes malware, then it's a $10K fine + $1 for every time that campaign was shown.