The search giant's targets are Web sites that use arbitrage to take advantage of loopholes in Google’s Adwords advertising system. Adwords allows Web sites to bid on the search terms beside which their advertisements will appear. The more demand for the search term, the more advertisers pay for each click on the ad that appears when users search for that term. The arbitrage scheme exploits that system using the basic buy low, sell high principle: A Web site arbitrageur uses a low-priced keyword to lure traffic and then redirects that traffic to another site that contains little content and is stacked with ads that earn a much higher price.

The more arbitrageurs like Schoemaker flourish, the more Google fumes. Arbitrage leads Google users to spam-like pages with nothing but more ads. That annoys users, says Google’s senior product director of ads quality, Nick Fox, translating to less trust for Google advertising and damaging the company’s integrity. “Adwords was founded on the notion that if users are happy, they’ll continue to click,” Fox says.

So Google has revised its page-ranking algorithm, the “spider” that constantly probes and indexes the entire Web, to give pages a “quality score” based on whether they appear to be content-less advertising pages or to have legitimate value. Pages with low quality scores are flagged by the spider and often must pay hundreds of times more for the same Adwords in Google’s auctions. Typical of Google, it has left the criteria for these scores a subject of mystery to prevent arbitrageurs from skirting the system.

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