There are actually some good people out there.

This is the story of how a financial trader discovered and reported on a Ponzi scheme ... that led to criminal charges and a long prison term for the perp. Interesting thoughts on how regulatory agencies do not work well until a lot of damage has already been done.

But he couldn’t do that. At the time, Mr. Schlobohm, now 37, was working as an informant for the Federal Bureau of Investigation. Wired to record Mr. Cook’s sales pitches and carrying a hidden camera, Mr. Schlobohm gathered evidence for at least four months as the Justice Department zeroed in on the scheme.

Mr. Cook pleaded guilty to mail and tax fraud last summer and was sentenced to 25 years in prison for orchestrating what ultimately became a $160 million swindle. William J. Mauzy, a lawyer who has represented Mr. Cook, did not respond to repeated requests for comment and for an interview with Mr. Cook.

That the authorities brought Mr. Cook to justice is undoubtedly a positive outcome. But Mr. Schlobohm’s journey as a whistle-blower, and some of the financial losses that still occurred even though authorities were closely monitoring Mr. Cook, also underscore the limitations of the system.