First, we must define what is online advertising. Online advertising is a CPM ad, which means the cost per 1000 impressions. Those who have the most money to spend on advertising, are the ones who have the most resources, and therefore those who are worthy of most of our attention.
The main problem of existing advertising networks with CPM models is that you may only target a single site. This makes CPM advertising almost impossible to deal with. You can also search the web to find the best cpm advertising network.
As a result, we use the CPC (cost per click), which has the advantage of automatic targeting thousands of sites. The solution to this problem is to use a system where advertisers can target multiple sites using CPM models.
This system can be done very easily by using the directory structure. Each publisher will submit his site in the appropriate category/subcategory and advertisers will be able to advertise at all sites under its categories and subcategories.
CPM ad network will show through several sites and charge for it. Just as the CPC system, except that the cost for clicks, not impressions. I will not go further on how this system should work, I'm sure they would decide to establish such a network, will know what to do.
The point is that in this way the network can serve relevant ads, even more, relevant than the best contextual networks.
For example, there is a network with a category called "Make Money Blog" and within this category, there are more than 600 blogs. Ads in all of these blogs with a single CPM campaign would be a great thing.