That is an interesting proposition, but I wonder what would fill the void created. I believe advertising does not increase consumption per-se, but that it redistributes it among a different set of product and services, so who would be the winners and losers of such an effort?
TV channels and magazines know how this works. If the page is about fashion, sell ad space to clothing companies. If the page is about travel, sell it to hospitality companies and tourism boards. If the page is about politics or finance, sell it to people making catheters and stair lifts.
It's much less creepy than trying to spy on everybody who reads the page, and then looking for an ad that fits your warped understanding of their preferences.
What kind of evidence are you looking for exactly?
At its simplest, it's the ad network deciding that you were recently seen visting toyota.com, so it'll show you 4 ads over the next hour for Toyota vehicles, to help cement that association. At its worst, it builds up an individualized profile over the course of months from thousands of websites (with google ads everywhere, you bet!) and allow advertisers to practically target viewers based on a psych profile.
Why do you believe this?