[duskwuff]

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.