This severely breaks down when you find a site you disagree with. Say you go on some anti-vaccines blog just to find after reading through a bunch of articles that they are a part of this program. Can you take your money back? Or what about a political campaign site for your rival? Or the Westboro Baptist clan?
Not for the majority (by number) of websites as you can not click on the ads. Websites tend to be a CPC model for all but the larger websites. Larger websites tend to mix CPM pricing with sponsorship & affiliate deals.
Yes, but psychologically most people won't think of ads in the same way as they would of the "thank you" banner you would see when contributing to the site this way.
It's still very small if it's one pageview in your entire month, and it's that fraction of a couple of dollars. I'd be surprised if this gets anyone significantly higher revenue than ads; that doesn't seem to be the goal.
I suppose that if you're running an appropriately-designed ad blocker (i.e., one that prevents Google's third-party ad cookies from reaching the site), then Google won't be able to route your contribution to the site, anyway.
I was thinking the same thing. I'd like the choice to rebalance my donations at the end of the month. Stackoverflow (if it were a charity) is immensely useful to my business while BuzzFeed isn't. If donations are proportional to clicks and time spent, the we maintain an incentive for clickbait and low-value content.