I was thinking about this further, and while it comes off as fairly irrelevant to start with, it's actually an extremely bad thing. In essence, this has set up two tiers of advertising: those we have paid for white list privileges, and those who haven't. This is heavily in Google's interests as they are the only advertiser powerful enough to get by with only text adverts - nobody else has a platform like Google searc…
The bad precedent was when Adblock introduced the concept of "acceptable ads" in the first place.
I believe requiring authentication, or requiring performing some prior action (such as watching/seeing an ad for some time period) are also examples of this.
I do not believe pop-under ads are subject to this. They try to force behavior (viewing of an ad) after the implicit contract is concluded (you are done consuming the media presented) through altering the state of items outside the presentation experience.
I think with the proliferation of ad blocking software, we've only allowed bad behavior to go unpunished more often by continuing to use resources that behave in irritating ways because a large portion of people get to skip the irritating behavior entirely. I think this has the dual negative consequences of not causing feedback for the behavior to reach the originator, as well as causing them to increase the behavior to capitalize more on those that are not immune to it.