The jury in the Tom Petters case was just starting its deliberations last week when federal regulators announced charges in a separate locally based Ponzi scheme involving a money manager and radio host. Although every new pyramid scam has a special twist or two, they're all made possible by the same blend of greed and trust that Charles Ponzi capitalized on to raise $1 million in three hours in 1921 by promising a 40 percent return in 90 days.

Petters, a Minnesota native who sold stereos in St. Cloud before building a house-of-cards empire in retail and other business ventures, secured a spot in the Ponzi record books Wednesday when a jury convicted him of orchestrating a $3.65 billion fraud over a decade. Jurors didn't buy the 52-year-old businessman's most important sales pitch -- that he trusted his underlings too much while he grieved the loss of his son John, who was fatally stabbed in Italy in 2004. Now Petters faces a life in prison, where he will have ample time to contemplate the pain he caused his victims, family, friends and employees.

Minnesota Attorney General Lori Swanson said she and her counterparts across the country have noticed an uptick in Ponzi activity during the Great Recession. Many of the victims were lured in by promises of big returns that looked even more attractive when traditional investments were slumping. You can almost hear the offers: "Lost a chunk of your retirement savings in the stock market? Here's a chance to get back on track quickly with minimal risk."

For some investors, Bernie Madoff provided a high-profile reality check. The Madoff scam prompted many to be more skeptical of promises of unusually high rates of return and creative investment products. Because Ponzi schemes rely on a steady flow of new dollars, skepticism is the last thing perpetrators want. These kinds of scams tend to unwind, Swanson said, when new dollars dry up and existing investors want to pull out their money. She recalled the classic quote from Warren Buffet: "It's only when the tide goes out that you learn who's been swimming naked."

There's been far too much skinny-dipping in Minnesota, and Swanson has noticed a common tactic: the use of relationships of affinity to build trust among investors.

Madoff tapped into Minnesota's close-knit Jewish community to lure investors, and soon word spread at Oak Ridge Country Club in Hopkins that members were getting great returns. Knowing that friends and associates are investing their money builds trust, Swanson points out, especially when returns are consistently strong.

Petters drew on his relationships with prominent Twin Cities businesspeople, luring sophisticated investors whose due diligence was based on trust and friendships instead of basic research. And one of his associaties, Frank Vennes Jr., who became an evangelist in prison, used his ties in religious circles to tempt several faith-based organizations to invest.

More recently, Minneapolis money manager Trevor Cook and conservative radio host Patrick Kiley were charged with operating a Ponzi scheme that defrauded at least 1,000 people out of more than $190 million. The alleged fraud was heavily promoted to like-minded listeners of Christian radio, which established trust, Swanson said.

"Con men in general are called con men because they build confidence in the investor," she said. "But here, a common thread through [the three cases] is a relationship of affinity to build that trust."

When the trust is broken, the kinds of investment scams operated by Madoff and Petters fall apart, leaving some of their victims' finances in ruins. To them, a few decades in prison must seem like a relatively small price to pay.