[joebadmo]

Ranking something lower, especially if it gets knocked off the first page, has the same effect in kind, if not degree, as blocking.

I'm not sure which part of this you think contributes to the filter bubble effect (which I'm skeptical about in the first place). If I block a site, it's because I don't want to see results from it, and I was never going to visit it anyway.

How is using blocking data as part of the algorithm any bigger a filter problem than any other part of the algorithm? Google uses many, many search signals and this is just one of them. And I imagine a pretty good one.