In current endorsement deals, its becoming harder and harder to discern where the celebrities end and their product and pitch begins. In the era of the human billboard, celebrities show up in about 14% of ads, more than double what it was a decade ago, according to researchers at Millward Brown.

Television programmers and music producers have become particularly eager to set up joint marketing deals that offer artists new ways to reach audiences, while also defraying their own marketing costs. Adding to the shift are celebrities who have also grown much more sophisticated about the structure and payouts of endorsement deals.

Early last year, marketing executives at Totes Isotoner, a Cincinnati company that had spent the previous 30 years churning out a reliable lineup of humble umbrellas, crowded around a computer and listened to a teenage singer from Barbados named Rihanna breeze through a tune titled, appropriately, “Umbrella.”

The song, not yet released, had commercial, jingle-ready lyrics and a stick-in-your-head hook: “You can stand under my umbrella, ella, ella, eh, eh, eh.” Totes, which hadn’t deployed celebrity endorsements since the former N.F.L. quarterback Dan Marino hawked its gloves more than a decade earlier, was smitten. “Umbrella” became a corporate rallying cry, with the song drifting through Totes’ offices at all hours.

Rihanna and her representatives wanted Totes to do more, however, than merely use her to peddle a product. They wanted Totes to create customized umbrellas featuring sparkly fabrics and glittery charms on the handles — all recommended by the emerging star and her team. Totes also guaranteed the singer a percentage of the sales of the umbrellas.

“Umbrella” went on to become a huge, Grammy-winning hit. And Totes, although it declines to discuss sales data, describes its relationship with Rihanna as “invaluable.” The company, which had never tried such a sweeping design shake-up before, says it now reaches younger shoppers and that traffic on its Web site — which links to Rihanna’s own site — has soared.

“We’ve worked hard to build me and my name up as a brand,” Rihanna says. “We always want to bring an authentic connection to whatever we do. It must be sincere and people have to feel that.”

But where the star ends and the product and pitch begin has grown less and less discernible in the era of the human billboard. Read more at [1] NYTimes