The "I've never heard of this ..." comment can also be explained by the possibility that the person making the comment is one of the fraudsters. This adds 10%

The "I've never heard of this ..." comment can also be explained by the possibility that the person making the comment is one of the fraudsters. This adds 10% to the 1/3 chance in your example. So no matter how high the rate of fraud is, we would expect to hear comments like this.