Many websites with pop-up ads (Forbes, etc.) display a 2-5s timer countdown to dismiss the ad and view the content, which engages users long enough to stay on the site. This games the bounce rate and would defeat a solution that is base solely on on it.
Users will bounce if they don't like ads, with or without countdown timers. Acting based on observed user behavior is great. If they don't like it, they bounce. If they tolerate it, they don't bounce. Over time, users will migrate to less-annoying sites. Ranking sites on observed bounced rates, whether caused by ads, low quality, or what ever else, is awesome and should have no anti-trust implications. That's not what google did.
After all, if these ads really annoyed users in general, that would show up in their behavior, and thus naturally be picked up on by ranking algorithms, no? (They annoy me, but I'm not all users.)
