There was no shortage of celebrity secrets for sale in 2009, with John Travolta, David Letterman, Cindy Crawford and others claiming they were victims of extortion.

From Letterman's monologue describing sexual liaisons with staffers to Travolta's emotional testimony about his son's death, celebrities confronted information and allegations that others offered to keep secret, for a price.

And those are just the cases that came to light. Experts say extortion is a constant threat to the rich and famous.

"For every one you hear about, there's probably 10 you don't," said Mark Geragos, a Los Angeles attorney who's handled numerous criminal and civil matters involving famous clients. "Just within the last three weeks, I've had two I've put to bed without anybody hearing about that would have been household names."

In the Travolta, Letterman and Crawford cases, the alleged attempts to get money backfired and resulted in criminal cases being filed. The past year's crop of alleged victims joins many other entertainers who have had to contend with extortion, including Elvis Presley, Bill Cosby, Michael Jackson, and Tom Cruise, to name a few.

Extortion statistics are difficult to come by. It can be charged under several different statutes at both the state and federal level. While some say anecdotal evidence shows extortion is becoming a more common tactic, the targeting of celebrities has been a constant problem.

"I don't think it's more prevalent," said Marty Singer, a Los Angeles entertainment attorney for more than 30 years. "In the last 10 years I don't think I've handled any more extortion cases than the previous 10 years."

Singer said he handles about one celebrity extortion case a month. He said the main difference now is that the financial demands are higher, and the people attempting to trade on the info are more aggressive. "It's sometimes the cost of doing business," he said.

Celebrity attorneys say that extortion attempts against their clients often involve information that isn't true. In some instances it doesn't matter if its release will hurt the entertainer's reputation.

"It's a different ballgame for celebrities," said David Shapiro, a former FBI agent and associate professor at John Jay College of Criminal Justice in New York. "Celebrities are especially vulnerable because they have an image."

A lot depends on the celebrity's reputation and how they want to handle the demands. "I have clients who couldn't care less if a sex tape comes out because they think it's going to make them more famous," Geragos said.