Twitter, which in its five-year existence has reshaped how people shop, vote and start revolutions, is now changing the business of celebrity endorsements.
A growing number of startup firms are hooking up companies with stars who get paid to praise products to their thousands, sometimes millions, of Twitter followers.
Singer Ray J received about $2,300 to urge his 600,000-plus Twitter followers to see the horror movie "Saw 3D."
Reality TV star Khloe Kardashian was paid about $8,000 to tweet about how Old Navy jeans make the Kardashian derriere look "scary good."
Experts say paying a celebrity to tweet is much cheaper than a traditional advertising campaign.
Of course, anything on Twitter is short-lived and reaches only a small, self-selecting audience: Research firm eMarketer estimates that only 11 percent of U.S. adult Internet users are on the micro-blogging site. And even though some celebs have faithful groups of followers, it can be hard to measure whether their tweets lead people to spend.
Still, celeb tweets can be a way to grab an audience at a time when many people skip TV commercials using their digital video recorders.
The Associated Press contributed to this report.