> Then you can't target the ads to those who most likely will buy, then each impression is worth less in most ad marketplaces. I don't think you will be able to suggest a solution if you ignore the true desires of the buyers and sellers of ads.

Their desires aren't the only factor in the equation here. If they want to satisfy their desire to have their ads seen at all, they're going to have to sacrifice some of their other desires. If they expect the user make all the sacrifices, then they shouldn't complain when users like me mercilessly block them, encourage others to do so, and do what I can to encourage regulation that would destroy them.

TV and newspaper only supported very granular targeting and the world didn't end despite that. You can still target based on context assuming the embedding site provides that information ahead of time.