Selling ads directly is the best when you've got the time and energy to do it. That's what I do on my site and it does produce higher returns.

We also got rid of Adsense a few months ago as the ads were generally of lower quality and didn't match the market of our publication all of the time (retargeting, etc). We also use only images for ads, as we try to have them be of magazine quality.

I'm sure some people visiting the site use Adblock etc but most advertisers are happy with the traffic they receive that losing a few views doesn't seem to bother them.

Without ad networks, pretty much only large and well-capitalized sites would be able to sell any ads at all.

If there is valuable enough ad space it wouldn't matter how large or well funded you are. The size of the site's audience is a factor but not the only one.

Still, some sites won't have a valuable enough space for ads. That's okay not every site should be able to get deals with ad companies. A good business shouldn't look like a get rich quick schema.

I disagree. To realistically sell ads directly to advertisers (or agencies) you have to be big enough to support a dedicated ad sales staff. And even if you have exceptionally valuable ad space, you have to be garnering enough impressions to make talking to you worth the advertiser's time. It would be impossible for many of the ad-supported websites and blogs I enjoy to earn dollar one from this approach.

That's clearly not true since in another comment here someone said they already do this and I doubt they're using a dedicated sales staff since they've mentioned dedicating time to it.

Regardless, it could soon be impossible to earn money with the other approach.

That would lead to lower rates because you can't prove your impressions. No honor among thieves.

Flip it and host all your content on the ad servers? Or at least some important parts, such that blocking them would make the site unusable?

Of course someone could startup a sniffer built to do nothing but prove impressions.

I've worked with a few companies that have used log files as proof of impressions to get around ad blockers. Every few months I would have to do wrong and disgusting things to the log files until the numbers looked like what they wanted to show customers. They don't trust each other to be honest.