I reckon you're right, but I doubt that it's manual or under Google's control. Google is too important a tool of control to be left in the hands of Silly Valley idealists.
I've always wondered why Sergey Brin and Larry Page retired when they did, it coincides almost exactly with the beginning of the SERP quality decline. Wonder what sort of conversation they had with intelligence to quietly walk to the door, cash out, and say nothing about the company since.
