Actually I think what it usually indicates is people aren't really responding to the truly hypothetical question (i.e. they aren't really taking it as read that the money is genuinely risk free). They are responding to the question "What if a bank OFFERED you 100% risk free money?" and basically indicating that they would be sceptical about the claim and that they would subsequently rather make 20% knwing they were in control of the risk.
Of course most people, offered really truly 100% risk free money would take it.
But how is that relevant in the context of a thread about a confidence trickster. Risk free it most certainly wasn't by the sounds of things....
GJ