Twitter is a blogging Web site that allows users to send messages of 140 characters or less.
Many film, TV, music and sports stars, as well as politicians, use the medium to get in touch directly with their fans.
Chris Romero, who goes by the name of Broadway and is the director of 50 Cent's Web empire, admitted he has tweeted messages on the rapper's behalf.
"He doesn't actually use Twitter," Romero told The Times. "But the energy of it is all him."
The newspaper said that many famous people employ similar tactics even though they are reluctant to talk about hiring ghostwriters to do their Twitter posting because it is supposed to be a direct connection to their devotees.
However, The Times said Spears recently advertised for help in creating content for Twitter and Facebook, and Kanye West told New York magazine he has hired two people to update his blog.
"It's just like how a designer would work," West said.
But basketball star Shaquille O'Neal doesn't agree with that theory and said he writes his own blogs.
"If I am going to speak, it will come from me," O'Neal said.
"It's 140 characters. It's so few characters. If you need a ghostwriter for that, I feel sorry for you."