CNET News.com: Groups push ad-tracking standard:

“The standard, called the Ad-ID platform, is a Web-based method for coding any type of ad linked to a digital delivery system, such as interactive TV or on-demand cable. Under Ad-ID, all advertisements get a 12-digit unique identifier that’s used to track them from creation to distribution. The identifier lets an ad agency and a distributor share data and lets ads be linked to analysis such as demographic data on people to whom the ads have been delivered.”