This is why US antitrust law focuses on harm to consumers, not companies. I don't see much harm to consumers if Google refuses to do business with websites that annoy consumers. Google already has a lot of rules that websites have to follow in order to be eligible for AdSense.
I don't know if that's true that it's an abuse of their position. Here's the paragraph from their policies:
> Sites showing Google ads should be easy for users to navigate. Sites may not change user preferences, redirect users to unwanted websites, initiate downloads, include malware or contain pop-ups or pop-unders that interfere with site navigation.
That all seems reasonable to me. They don't want to be associated with garbage websites.
And my personal opinion is that this kind of thing is exactly what G should be doing with their market position.
No consumer, anywhere, in the history of ever, has wanted things to pop under their browser window stealthily. As such, G abusing their position to hurt companies that do it is a good thing. Those companies should be hurt, and preferably die a terrible, terrible death.
If and when G uses their market dominant position to do something which hurts consumers, then things should be investigated. But an action like this, which has no negative consequences for users, should be applauded.
Google AdSense already has a bunch of requirements in place for sites that want to run their ads -- content restrictions, restrictions on traffic sources, limits on the number of ad units on the page (including ads from other networks), etc. Many of these restrictions are in place because Google's advertisers won't want to run their ads on pages that don't meet those requirements, and Google's new limitations on popunder ads probably fall into that category as well.
Google banned my site from their index! Antitrust regulators need to look into this because it costed me my business and my employees! </sarcasm>