I've been thinking about this as well. As Google search results get increasingly worse, I find myself subconsciously filtering out all the garbage and gravitating towards a small number of known sites; and, as many other HNers do, I frequently mitigate this filtering step altogether by adding add "reddit" to any search in which I'm seeking out real human sentiment.
I've done similar optimizations elsewhere to counter Google's trash results, e.g., I've been beefing up my personal recipe database, with the goal being that I can avoid a google search altogether whenever possible, only hitting google as a last resort.
More and more I wonder, with the modern internet, is it even a feature that the whole web is indexed? Might be a bug.