The real money for Google is in adwords. Search for something and see how many big brands are in page one and how many of them are advertisers as well.
And then google 'Vince Update.' It's not directly a Google search engineer checking to see how much, say Geico spends on Google vs Allstate, and adjust ranks accordingly. But it works close enough as the bigger brands spend more in ads, internet included.
It started just for major keywords like electronics, insurance, jewelry etc, now Google is giving them even long tail searches since the Mayday Update. Panda, IMO, gave them even more.