NEW YORK (MainStreet) -- When the history of advertising in the 21st century is written, one gimmick from a little-known advertising group named Adzookie will likely come to be viewed as a watershed moment when the traditional notion of ad space was upended in favor of a new form of product placement. In early April, Adzookie, a small company in Orange, Calif., presented homeowners with an extreme promotion: If they agreed to have a temporary Adzookie advertisement painted on their house, the company would pay the mortgage each month the ad stayed up (and cover the cost of painting the ad and repainting the house afterward).