With the rise of online multiplayer games and worlds, collecting virtual goods has become an increasing social activity and therefore established the virtual goods subset of virtual collectibles as a relevant category. The corresponding emergence of virtual markets leads to increasing economic and social relevance for virtual collectibles. This is not only true for the obvious markets in virtual worlds where operators try to maximize the economic impact for them and develop sustainable business models. It is also true for many activities in real and virtual worlds where virtual collectibles...