"Over time, as people tend to click one version of ad text over others, the weights change, " Prof Sweeney explained.

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Categories are based on actual Google.com search terms and are matched up against your keywords, ad text, and landing page text.

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But doing so will be more complex--both for Google and its customers--than simply crafting an effective AdWords text ad.

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Will people share organic search results or a text ad?

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But doing so will be more complex--both for Google (nasdaq: GOOG - news - people ) and its customers--than simply crafting an effective AdWords text ad.

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To prove the market interest, the quartet had set up a Google AdWords campaign, spending a couple of hundred bucks on a text ad that ran next to searches for dentists, hair salons and landscapers.

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They were still a single-digit percentage of text search ad clicks, about 6%, but Google only rolled them out widely in October.

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Text-heavy magazine ads from Omnicom ad agency BBDO Detroit will explain how small diesels work.

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The whole arrangement, particularly that last part, was terrifying to publishers, who saw an ad-revenue future burned away in a stark landscape of text-only syndication.

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By giving away its site's traffic in exchange for more video views, Google is likely betting on the future of "in-stream" advertising--video ad clips or pictorial ads overlaid on videos--rather than the display ads or text ads that typically appear on Google's sites.

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