In this issue we pursue our exploration of whether and how digital platforms, especially digital platforms as applied to the network industries, should and could be regulated. Indeed, as of recently, attention paid to these emerging digital platforms is exploding. Most of the related publications aim at making recommendations as to whether, and if yes, how to regulate these digital platforms in the interest of the consumer, the citizen, the public economy and even public values. Some of these recommendations may be drawn quite hastily, triggered by scandals and other (geo-)political considerations. The four contributing authors, all professors, will take a step back and look at where we stand in terms of the more academic debate on digital platforms, especially on these platforms that clearly have public (service) implications. In turn, they will apply economic, competition, legal and political perspectives on the regulation of digital platforms and try to derive from there the current state of the debate. In particular, they want to crystalize what we already know – and therefore have sufficient reasons to regulate – and what we do not know yet. In short, this issue should serve as another contribution to the current debate about the regulation of digital platforms, in particular digital platforms applied to infrastructures and public services.