Our friends at @AdMaven just sent out an interesting email:
I agree 100% and that's why I'm very focused on push notification traffic right nowThe rise of new ad formats such as Push Notifications is getting more and more significant. This week Google announced that starting next month they are expending their adblocking campaign to block another ad format - https://blog.chromium.org/2018/11/further-protections-from-harmful-ad.html
Due to this expansion and the fact that Google is tightening their adblocking efforts on different ad formats, the traffic you used to buy from several specific channels will decrease. That is why new compliant ad formats are emerging.
Push Notifications, Interstitials, and Native Ads have already gained a lot of momentum in 2018 and are now the focus of many advertisers' budgets, up to the point where a lot of advertisers are employing dedicated media buyers only for these ad formats.