The ongoing financial crisis is the consequence of the evolution of the international financial system. This evolution has led in a short time period to one of the most remarkable cases of productive diversification, globalization and concentration of banking activities: a growing complexity of an unusual extension. The financial sector presents few peculiarities, generally recognized, that suggest to control and drive the behavior of its operators, with the purpose to limit their risk-taking in order to safeguard the common interest. The first of these peculiarities is the fiduciary nexus that accompanies the relationships with customers; this nexus needs to be recognized and safeguarded. The aim of the Supervisory Authorities of each country and of any supranational organism is to establish and fix, timely, monitoring and regulatory systems on the behavior of the financial operators, with the aim to forbid the diffusion of selfish and opportunistic trends that lie at the basis of any fiduciary crisis.