Google Contributor is (was?) a good idea, and for a while I really enjoyed using it. It was nice to visit a page and see the "thanks for being a contributor" messages instead of visually aggressive ads.

Of course it was canceled at some point, and now it looks like there is some meager effort to require sites to opt-in somehow.... I can't tell if any sites have actually done so.

Too bad, because I really liked the old experience.