If you think Bernie Madoff or Allen Stanford were the only Ponzi operators hard at work fleecing investors in the past few years, think again.

The Securities and Exchange Commission and FBI have seen Ponzi-scheme cases soar this year, even if many of those cases don’t get the kind of attention that the multibillion-dollar con jobs have received.

The amounts of money involved in the Madoff and Stanford schemes are, of course, truly monumental. Madoff swindled an estimated $65 billion from thousands of investors over the course of two decades before the whole house of cards came tumbling down last year as the economy crashed and the money to pay off old investors with new money dried up. Now Madoff is serving a monumental prison sentence—150 years. Stanford is accused of running a $7 billion scheme involving fraudulent certificates of deposit.

But in a more quiet way, the number of other Ponzi schemes—some of them involving some pretty big numbers themselves—that have come to light this year is just as staggering. In fact, you could call 2009 the year the Ponzi bubble burst. The contracting economy hasn’t just hurt legitimate businesses. It’s made it tough on Ponzi fraudsters as well. They rely on new investors to pay old investors, and new investors have made themselves scarce as a result of the contraction.

The FBI has 632 open cases of Ponzi schemes or high-yield investment fraud so far this year, said David Nanz, chief of the Economic Crimes unit at the FBI.

“It’s a dramatic increase,” he said. In all of 2008, the FBI handled 429 such cases, and in 2007, it handled 389.

Ponzi schemes are pyramid schemes named after Charles Ponzi, who in the 1920s duped thousands of New England residents with the promise that he could bring in big returns by investing in foreign stamps. He used money from later investors to pay off some early investors.

“The Ponzi schemes have always been with us,” Nanz said. “We have seen a dramatic increase in identifying them as they collapse.”

He attributes the increase to the economy. As the economy worsened, Ponzi operators had a harder time drawing new investors, and their schemes collapsed.

“When the tide goes out, you see who’s not wearing their bathing suits,” Nanz said.

The SEC filed more than 40 cases involving Ponzi-like activity from January through August 5, Robert Khuzami, the director of the SEC Division of Enforcement, said in a speech to the New York Bar Association. The division brought about 70 enforcement actions in 2007 and 2008 combined.