Madoff is the exception rather than the rule--and even Madoff operated his Ponzi scheme for over 40 years before being prosecuted.

Madoff's arrest and prosecution was actually pretty ineffectual in my opinion. If an amoral person can live as one of the richest men in the world for 40 years in exchange for spending the last 10 years of their life in minimum-security prison, I think a lot of amoral people would take that trade.