As advertising has moved online, the way companies buy space for it has also changed. The New York Times has outlined the rise of "programmatic buying," an automated ad system in which tracking consumers has become as important as making sure the ad matches the site's tone. Ad space buyers look not for certain kinds of places, but certain kinds of viewers, often following them across multiple sites. "Accessing media is a commodity now," says digital advertising executive Sheldon Gilbert. While Do Not Track and other privacy efforts promise to take data out of advertisers' hands, the Times indicates that tracking-heavy, algorithm-based buying is here to stay.