Google's service to me, the customer, is fast, useful search results. There is no way they've confused their real customers for spam sites... that's just too short-sighted and there are zero barriers to people switching if a competitor with better results came along. But here's what I don't get: Lots of companies implement customer feedback to improve their services. I can't decide why Google hasn't done some sort of browser plugin (or other approach) that allows you very simply thumbs down a site when it's a not useful result. Enough negative feedback from real users and a site could be demoted in organic search. Is that just too hard to build in a way that couldn't be easily gamed?

Edit: I know they experimented with voting arrows on the results page and I'm curious why some variant of that hasn't been deployed more widely.