This paper is based on the hypothesis that digital business can only be conducted once the necessary institutional framework has been put in place. Trust – the cornerstone of all business activity – is an indispensable prerequisite to such a framework. This trust is created on the one hand by technology and, on the other hand, by institutions such as banks. And trust is one area in which the banks in particular – despite the threat of disintermediation and their precarious position in the world of e-commerce, brought about by services with such a substantial information content – can tap a vast store of marketing potential. The original reason why banks emerged several hundred years ago was an attempt to mediate between certain market imperfections and conflicts of interest. Banks are, therefore, institutions whose position in society has been built on precisely these imperfections. Accordingly, the banks in today's digital economy will only be able to escape the threat of disintermediation if they once again adopt the role of "business enabler". They will be able to hold their own on the market only if they assume the function of a "trust mediary". This hypothesis derives from analyses of transaction cost theory, but is also based on two empirically representative studies conducted on the subject and which, given a conjoint analytical approach, permit concrete market simulations to be derived. From the point of view of Internet users, such simulations describe the role of the banks as trust mediaries who will in future operate in three dimensions: transformation, transaction cost reduction and trust.