meleva
Click fraud is what makes Tier 2 CPC networks really risky for advertisers even if CPC are much lower than Tier 1 (Adwords, Bing).
Regarding your Adsense example, was there not a mention like "Ads by Google," "Sponsored Links," or the AdChoices icon ? In that case, it makes clear that it's not a natural link.
You own a website, I own a website. I pay you $100 to show your visitors a link to my website. The link is presented as an organic, non paid link. =BAD
You own a website, I own a website. I pay you $100 to show your visitors a link to my website. The link is presented as a paid link, with a no follow attribute. =GOOD
On a side note, your breakdown of the Ad Revenue using Google as a middleman is wrong. If you pay Google 100$ (via Adwords) to decide to show ad on my site, I will get 68% of that 100$ and Google will get 32%
Adense revenue share: https://support.google.com/adsense/answer/180195?hl=en
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