I doubt there's a definition of "ad" that would be feasible target on a platform like Youtube. A trailer, for example, is an ad for a movie, but I think Youtube

I doubt there's a definition of "ad" that would be feasible target on a platform like Youtube. A trailer, for example, is an ad for a movie, but I think Youtube would be harmed if all of the upcoming movie trailers were removed. As a consumer, I find it pretty easy to distinguish between a "wanted" ad and an "annoying" ad, but I don't think there's a way to enforce rules based on user value systems if for no other reason than every user's value system is going to be distinct.