My latest Guardian column is "Google admits that Plato's cave doesn't exist," a discussion of how Google has changed the way it talks about its search-results, shifting from the stance that rankings are a form of pure math to the stance that rankings are a form of editorial judgment.
Google has, to date, always refused to frame itself in those terms. The pagerank algorithm isn't like an editor arguing aesthetics around a boardroom table as the issue is put to bed. The pagerank algorithm is a window on the wall of Plato's cave, whence the objective, empirical world of Relevance may be seen and retrieved.
That argument is a convenient one when the most contentious elements of your rankings are from people who want higher ranking. "We have done the maths, and your page is empirically less relevant than the pages above it. Your quarrel is with the cold, hard reality of numbers, not with our judgement."
The problem with that argument is that maths is inherently more regulatable than speech. If the numbers say that item X must be ranked over item Y, a regulator may decide that a social problem can be solved by "hard-coding" page Y to have a higher ranking than X, regardless of its relevance. This isn't censorship – it's more like progressive taxation.