bernard madoff?" and they all said, "no. we don't think he's for real." >> kroft: could you find anybody? >> i found no one that ever traded with mr. madoff, and i traded with the largest equity derivative service in the world. >> kroft: and that's because madoff's investment fund never actually made any trades, at least going back to 1993 and probably further, a fact confirmed at a meeting of madoff investors by the trustee charged with liquidating his assets. no one knew the depth of the fraud, but a lot of people had questions. who else figured this out besides you? >> i would say that hundreds of people suspected something was amiss with the madoff operation. if you look at who the victims were not, you'll notice that the major firms on wall street had no money with mr. madoff. >> kroft: i mean, you write-- this is the letter. i'm quoting from the letter to the securities and exchange commission, red flag number 20: "madoff is suspected of being a fraud by some of the world's largest, most sophisticated financial services