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.

Only in a very, very small and indirect way. And you can solve that problem by installing and ad blocker and whitelisting sites.

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.

At some fraction of $3/month, you aren't going to be giving those sites much for a single impression or two anyway, sounds like.

I wonder how hard it would be to block the script/call on sites you don't want to support (or just whitelist it on ones you do). I'd imagine not very.

There will almost certainly be a way to block Contributor the same way you block ads.