[summerdown2]

My understanding is that adblockers work by removing known third party app sites from loading items on a page.

If that's true, what would stop a website from proxying ads, so they appear to come from the website rather than the third party?

I guess that would involve more bandwidth and so less money for the site, but high-bandwidth items are the ones people complain about anyway. I don't see why text based ads would be impossible under that scheme, for example.