Google provides a lot of this data to advertisers -- so they bid for more word combinations.
Even though Made-For-AdSense microsites are polluting the infosphere, in the short term they probably even make Google money. Overstuffing natural results with repetitive, poorly-written information? Great, you're more likely to click a paid ad instead! Making it so all the top 10 natural results are AdSense-holding pages? Great, no matter where you go, you might click a Google ad!
Making it so all the top 10 natural results are AdSense-holding pages?
Actually, that's probably the one area Google won't go for, but it results in a smaller pool of people to make money off of, as consumers can't get the right answers to their questions.
The key needs to be high-quality content delivery. Without that, you leave yourself vulnerable to being banned.
Yet: there's an inherent tension. Unless there's a credible threat people will go to another engine for natural results, for Google to degrade their own natural results slightly can improve Google's quarterly revenues!
Let's say Google is A/B testing a ranking tweak. Option A results in more searches (because people don't find exactly what they're looking for on the first try), and more clicks on ads (because they look relatively better). Option B results in one click on a natural result and nothing further.
Are we sure they'll always choose option B?
Maybe Google can add a new advanced operator: [-src:googlesyndication.com]. That is, don't return results that 'source' (as in <SCRIPT SRC="">) Google ad units.
Even though Made-For-AdSense microsites are polluting the infosphere, in the short term they probably even make Google money. Overstuffing natural results with repetitive, poorly-written information? Great, you're more likely to click a paid ad instead! Making it so all the top 10 natural results are AdSense-holding pages? Great, no matter where you go, you might click a Google ad!