[georgeott]

Who counts the impressions, to pay the ad client?

[dredmorbius]

There are other bases for compensation. Conversions / actions / clickthroughs.

Measure what you can see. Don't obsess over what you cannot.

[vortico]

Good point, I had this question earlier about ads in general, but this didn't even pass my mind.

[untothebreach]

Idea: ad network w/ a daemon the publisher installs in their infrastructure between the users and the content. Maintains a blockchain which verifies exactly how many impressions there have been.

[knd775]

OP probably means major publishers who can solicit advertisers more directly.

[johnward]

Which tend to still use 3rd party ad severs. Probably because they don't want to develop that tech in house.