  Recent research in industrial organisation has investigated the essential
place that middlemen have in the networks that make up our global economy. In
this paper we attempt to understand how such middlemen compete with each other
through a game theoretic analysis using novel techniques from decision-making
under ambiguity. We model a purposely abstract and reduced model of one
middleman who pro- vides a two-sided platform, mediating surplus-creating
interactions between two users. The middleman evaluates uncertain outcomes
under positional ambiguity, taking into account the possibility of the
emergence of an alternative middleman offering intermediary services to the two
users. Surprisingly, we find many situations in which the middleman will
purposely extract maximal gains from her position. Only if there is relatively
low probability of devastating loss of business under competition, the
middleman will adopt a more competitive attitude and extract less from her
position.
