"White collar" criminals are often people who got a little too inventive when they came up with ways to make money. Their creativity was not appreciated by the authorities, who insisted on things like obeying the laws and such.
Also, they often find that the prison environment is different than what they have been used to. At the very least, they find their position in that environment is different -- without their wealth they may not have the power they've been used to having in a society where individual strength and connections are measured differently than they are in the boardroom.
So leave it to these entrepreneurs to figure out how to make a buck off having been in prison -- by offering advice and guidance to the white-collar criminal types who are about to go there. This Wall Street Journal piece tells the story of how one particular man convicted of fraud is learning what to do and what not to do in prison. The guides range from the courtesy of ordinary interactions (always say, "Excuse me" if you bump someone) to how to survive high-intensity confrontations that could result in injury or worse.
Ol' Ms. Free Market is an inventive kind of gal, isn't she?
(H/T Jonathan Last)