The recently adopted Eu's Regulation on multilateral interchange fees for card-based payments (hereinafter «Mifs») changed the very nature of public intervention in the markets of payment cards through the introduction - aside of the traditional "ex post" antitrust intervention - of an "ex ante" regulation. Mifs represent one of the main areas of intervention by antitrust authorities within banking services, both at the European and national level, due to the risks of restricting competition deriving from the joint determination of such competitive variable. The paper - after having reviewed the evolution of the antitrust approach to Mifs within the broader framework of two-sided markets - provides a description of the reasons underlying the Eu Commission's decision to adopt a proposal for a Regulation. Moreover, the prerequisites for a Mifs regulation will be analyzed, in terms of the identification of an appropriate market failure, as well as the risks of a regulatory failure connected to the way EU's Regulation has been defined in practice. In conclusion, the paper highlights the need to focus more on the efficiency of the system introducing - for example - a higher degree of flexibility in the practical implementation of the regulatory model adopted. In such context, technological innovation - in terms of e-payments and m-payments - may enable the development of new business models that do not rely on Mifs.