The bottom line is that Google wants to pick the winners and losers on the Web, as opposed to being a vehicle for the Web that wants to be built. Not very "free market" of them, and why we'll see continuing legal trouble for Google. The truth will out.
On one hand, I feel for and understand Google's efforts to display "quality", "relevant results". The problem is the gigantically stupid ways they tend to go about it.
WTF is "over-optimization"?!? ...it's an oxymoron. SEOs are doing nothing other than showing Google bot what it implicitly wants to see, 99% of the time doing nothing that implicitly, and expressly goes against Google's TOS.
While Google must certainly keep proprietary secrets, the only logical purpose behind being so utterly vague about what actually constitutes acceptable SEO, "quality" and "relevance" is to maintain dictatorial control of how the Internet develops over time; and, to pass the buck to the very people that give them the Internet - website owners, SEOs and webmasters.
For me, there are two types of people in the world: Those who have no problem with Google "taking care" of everything as concerns search results; and, those that understand at an almost primal, gut level that the very notion of this is absurd, if not dangerous.