That wouldn't be the worst future though. In my head, once the adverts are being hosted on the website domain, there'd be a lot more incentive to a) NOT deliver malware, and b) NOT have those wearisome video/sound/flashing/js-heavy adverts.
It is much harder to get the site whitelisted once it has been compromised since it is on the same domain.
In my job, we had a site domain that was falsely flagged as malware-infected and it took about a few days before it was confirmed as removed (it is not automated apparently). It was never made clear why it was flagged in the first place but it scared us and we had to isolate any downloadable files (installer, ads, etc) away from the main domain as much as possible.
I don't remember third party domains being problematic to remove compared to the first party stuff?