The early Buffet partners were never told what their money was invested in. They trusted that WEB was honest. Madoff was trusted by his investors and when they got their statements, they had no reason not to beleive them. Also, don't forget people assume the SEC is looking out for them and that a crook will be caught. That is always the problem with government oversight of anything (food, medicine, product safety, investing, etc), people trust that oversight and look no further. The only thing his investors are guilty of is trusting too much and maybe laziness and a little stupidity, none of which are crimes. He is guilty of fraud on a grand scale, which is a crime. If someone is unarmed in a bad neighborhood at night taking money out of an ATM, he may be stupid, but no one has a right to kill him and take his money. Making yourself an easy mark, does not justify the crime against you in any way. Fraud and theft are crimes and the person committing them is solely responsible for them, regardless of how easy or difficult the victims are to steal from. Have you ever heard a defendant say, "sure your honor, I kidnapped, raped, and killed the little girl, but it was just so damn easy to do. Surely I can't take all the responsibility.". Madoff is the one who bears responsibility for his own actions. If anyone else is to blame other than him it is the SEC for not doing its job and letting this go on for so long.
--Eric