At the beginning of the Accord revision process, many risk managers assured regulators that the art of credit-risk modeling was advanced and that there was broad consensus. However, upon further investigation, regulators--and I believe many practitioners themselves--have discovered that there is less rigor and less consensus than had appeared to be the case initially.
Such diverse views and practices reflect the ugly fact that the devil is in the details of model parameter values. This lack of agreement, together with the associated uncertainty, is not just a problem for the regulators.