An interesting experiment is to look at every link on the search results page and try to figure out how many don't generate cash for Google, its getting harder to find more than one, yet when Google was started it only profited from the ad-links.
As others have mentioned search has changed. There is no longer a big push for 'finding things on the web' which was the appeal of early search engines, now the bulk of the web use search as their portal to a giant reference library and product catalog. One of the things Google tried to monetize and failed was reference information (Knol) so now more and more they just show you the fact you were looking for, scraped from some web page, right on their page, no need to click away.
I think it was a smart move on their part from the shareholder perspective (disclosure I sold all my Google stock at $650 :-(). The second order effects though will be interesting. You see if Google becomes just a catalog, sort of like SkyMall "Magazine" in airplane seats, then it risks losing all of its unique utility. I'm certain that Microsoft can construct an equally compelling catalog as can Yahoo. This will shape the future for them.