There are two economists – one young and one old – walking down the street together.
The young economist looks down and sees a $20 bill on the street and says, “Hey, look a twenty-dollar bill!”
Without even looking, his older and wiser colleague replies, “Nonsense. If there had been a twenty-dollar lying on the street, someone would have already picked it up by now.”
Libor manipulation was on the public record years before the scandal blew up. Exposing anything but dirt-simple financial fraud is hard, even to people who know all the facts.
Malcolm Gladwell has a great piece about how all the information needed to piece together Enron's fraud was always available in public records. Worth a read.