1.1 Motivation Today's transportation market is far from perfect. Market participants have admission only to a certain fraction of the market and price formation lacks transparency. However, this state is no law of nature since in principle, all market participants could manage to get together somehow and do business - but gaining new business partners beyond existing bonds usually takes too high efforts. After all, the items in transportation markets are usually traded under extreme time pressure: transportation orders have fixed pick-up and delivery deadlines and free transportation capacity cannot be used thereafter. Here, Internet-based freight markets promise help. Since the early 1990s many of such markets have come into existence so that a considerable number exists today. For Germany alone, over 50 different electronic transportation marketplaces are listed in a database hosted at the University at Bremen (2001). The mediation models of these marketplaces are quite diverse (cp.