Hi bigtel,
I'm actually new to this industry, but what I think is that, the bounce rate can be a major factor to take into consideration. Let's take an example...Say there is a wesbite that could deliver an amount of 1-2 Million impressions in a month. But the page views are low, and the bounce rate is high, visitors don't spend enough time on the website to actually explore what contents/articles the site has. Therefore, they are least bothered about all the ads running there, since they just want to see whether the site has the content which the visitor is looking for. For some campaigns, the webmaster places ads in the inner articles...but that goes to waste now, since the visitor is not interested in the website no more. Hence, it will reflect on the CTR/CR/Revenue.
Please share your views, and should you find some of my info incorrect, please do correct me. I'd like to improve my knowledge in this industry.
Have a good one bigtel!