Celebrities for sale? A New York Times columnist questions the ethics of stars who endorse junk food.

• Position: OPINION

Marketers have long understood the power of celebrity endorsements.

In the 1760s, Josiah Wedgwood, owner of the Wedgwood pottery company in England, used images of the royal family to add cachet to his chinaware. In the 19th century, Mark Twain lent his image to cigar and flour brands. And in 1948, long before he was president--and before the dangers of smoking were fully understood--actor Ronald Reagan posed for a Chesterfield cigarette ad.

Today, celebrities loan their names to everything from perfume to cereal. But some people think that stars should be more discriminating about what they vouch for.

In this op-ed piece, New York Times food columnist Mark Bittman takes aim at celebrities who promote unhealthy food products like sugary drinks. In particular, he argues that Beyonce's recent multi-year deal with Pepsi is ethically questionable because of the mounting evidence linkinq soda to obesity and diabetes; Bittman's criticisms could just as easily apply to other celebrities endorsing other unhealthy products.

Read the piece, then decide for yourself: Should celebrities be more picky about what kinds of products they endorse?

Beyonce Knowles would presumably refuse to take part in an ad campaign for guns. But she's eager, evidently, to have the Pepsi logo painted on her I lips and have a limited-edition Pepsi can bearing her likeness.

You may have seen her on February 3 on the Super Bowl Pepsi halftime show, where she was to be introduced by 50 of her luckiest and best-gyrating fans, who were selected through a contest.

For this and other efforts, Pepsi has spent $50 million, part of which will support her "creative projects." And unless she's donating some or all of that money, this is an odd move for a politically aware woman who, with her husband, Jay-Z, raised money for President Obama and supported Michelle Obama's Let's Move campaign, meant to encourage children to exercise.

Knowles is renting her image to a type of product that may one day rank with cigarettes as a killer we were too slow to rein in. From saying, as she once did in referring to Let's Move, that she was "excited to be part of this effort that addresses a public health crisis," she's become part of an effort that promotes a public health crisis. I suppose it would be one thing if she needed the money or the exposure, but she and Jay-Z are worth about $775 million.

Nor is she alone: The list of soda shills has ranged from LeBron James and Madonna to the...