The headlines say things like “Laser Hair Removal,” “Christian Singles,” “Turn Traffic Into Money,” “Have You Been Injured?” “Belly Fat Diet Recipe,” “If U Can Blog U Can Earn,” “Are You Writing a Book?” and so on. Countless M.F.A., or Made for AdSense, Web sites have appeared; they use articles stolen or “scraped” or mashed together from sites like Wikipedia, and their edges are framed with Google’s text ads. The ads work on a cost-per-click scheme: the advertiser pays Google only if you actually click on the ad. If you do, he’s billed a quarter, or a dollar, or (for some sought-after keywords like “personal injury” or “mesothelioma lawyers”) $10 or more.

But think — when was the last time you clicked on a three-line text ad? Almost never? Me neither. And yet, in 2008, Google had $21.8 billion in revenue, about 95 percent of which flowed from AdWords/AdSense. (A trickle came from banner and video ads sold by Google’s new subsidiary, DoubleClick, and from other products and services.) These unartful, hard-sell irritants — which have none of the beauty or the humor of TV, magazine, radio or newspaper advertising — are the foundation of Google’s financial empire, if you can believe it. It’s an empire built on tiny grains of keyword-searchable sand.

The advertising revenue keeps Google’s stock high, and that allows the company to do whatever it feels like doing. In 2006, when Google’s stock was worth $132 billion, the company absorbed YouTube for $1.65 billion, almost with a shrug. “They can buy anything they want or lose money on anything they choose to,” Irwin Gotlieb, the chief of GroupM, one of Google’s biggest competitors in the media market, told Auletta. If Microsoft is courting DoubleClick, Google can swoop in and buy DoubleClick for $3.1 billion. If the business of “cloud” computing seems to hold great promise, Google can build 20 or 50 or 70 massive data centers in undisclosed locations around the world, each drawing enough power to light a small city. Earlier this month, Google announced it would pay $750 million in stock for a company called AdMob, to sell banner ads on cellphones. “Once you get to a certain size, you have to figure out new ways of growing,” Ivan Seidenberg, the chief executive of Verizon, said to Auletta. “And then you start leaking on everyone else’s industry.” That’s why Auletta’s C.E.O.’s are resentful.

True, the miracles keep coming: Google Voice, which can e-mail you a transcript of your voice mail messages; and Chrome, a quick, clever Web browser; and Android, the new operating system for mobile devices. One of the latest is an agreement to print books on an A.T.M.-style on-demand printer, the Espresso Book Machine. But perhaps there are too many miracles emanating from one campus now; perhaps brand fatigue is setting in. Google’s famous slogan, “Don’t be evil,” now sounds a little bell-tollingly dystopian.

When they were at Stanford, Page and Brin criticized search engines that had become too “advertising oriented.” “These guys were opposed to advertising,” Auletta quotes Ram Shriram, one of Google’s first investors, as saying. “They had a purist view of the world.” They aren’t opposed now. Now they must be forever finding forage for a hungry, $180 billion ad-maddened beast. Auletta describes an unusual job-interview test that Sergey Brin once gave to a prospective in-house lawyer: “I need you to draw me a contract,” Brin said to her. “I need the contract to be for me to sell my soul to the Devil.” That was in 2002, the year Google began work internally on what would become AdSense.

Now Page and Brin fly around in a customized Boeing 767 and talk sincerely about green computing, even as the free streamings of everyone’s home video clips on YouTube burn through mountaintops of coal. They haven’t figured out a way to “monetize” — that is, make a profit from — their money maelstrom, YouTube, although I notice that Coffee-mate and Samsung banners appear nowadays in Philip DeFranco’s popular video monologues. “The benefit of free is that you get 100 percent of the market,” Eric Schmidt, Google’s chief executive, explained to Auletta. “Free is the right answer.” For a while, perhaps — but maybe free is unsustainable. For news­papers, Auletta writes, “free may be a death certificate.” Maybe in the end, even on the Internet, you get what you pay for.