"Thus we want to suggest an approach to watching customers that is less expensive and more expansive: Watch what a hypothetical customer would do. Since the customer is imaginary, this approach brings the costs way down. To encourage expansive thinking, we give our hypothetical customer extremely large resources -- if there is a solution to the problem, this person can find it. In short, we ask, What would Croesus do? "
This intially struck me as a strange variation on personas... rather than design for the least able, we start with design for the most able....