Earlier quoted context omitted.
>Isn't the original PageRank (...) defined by what Google engineers believe to be a relevant and informative webpage? No, quite the opposite. The original PageRank was defined by what other internet publishers considered to be a relevant and informative webpage. Specifically, the original PageRank was weighting content by the links (and content around the links) it was getting. The trust was placed on the internet pu…
Right, I understand your point, and maybe I'm being too reductive here, but the idea heuristic that what people link to is authoritative is an opinionated decision that ended up being satisfactorily accurate (and efficient to implement). And evaluating the heuristic's accuracy ultimately boils down to human judgment; from their early Google proposal (though not the original Pagerank paper): http://infolab.stanford.ed…
There are two decision spaces here. One is the selection of search ranking algorithm (whether to use PageRank or any other), and that decision was taken by Google[1].
The second decision space is the decision whether to link (or not) to any given document, and what content to put around it. That is a long lasting iterative process rather than any singular decision. Arguably it's geared towards approximating the distributed consensus - which is a global mutable state; expressed with edges the graph rather than any singular node.
Can the process be gamed, perverted, or corrupted randomly or maliciously? Sure. Do we know any better one? Not yet, at least not in the public.
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[1] practically speaking we all selected PageRank, by preferring Google's over multiple competing engines.