Last year the CEO of media-buying shop GroupM, a division of the ad conglomerate WPP Group (WPPGY), quietly directed more than 16% of the world's $364 billion in global ad expenditures. He not only understands media better than most; he has the power to sway the industry to his vision. And lately that vision entails old media taking lessons from the web. "Say you want to sell grapefruit," he says over an egg-white omelet at London's Four Seasons, where he keeps an extra set of clothes for regular visits. To move a lot of citrus in the traditional way, he explains, you'd buy a spot on "Grey's Anatomy" or run an ad in Vogue, making behavioral assumptions and inferences built on viewer demographics. But in the digital world, ad buyers don't need to assume anything; they have data to work with. Online marketers track actual behavior, so instead of buying a type of audience, they can buy a click, an inquiry, or even a sale. Every time consumers take such an action, it becomes part of their "clickstream," which follows them around the web. This information trail gives marketers an increasingly sophisticated idea about each of us, allowing them to craft an ever more tailored online experience.
But why stop there? What the business really needs is a venue with the reach of old media and the data trail of the web. In 2006, GroupM placed, tracked, and measured 200 billion online impressions
