Technology developments such as Web Services, GRID Computing and peer-to-peer toolkits are rapidly changing the way systems deployed in public networks interact. Large-scale usage of these technologies would very likely lead to environments which have many of the features commonly considered in Agent mediated e-commerce research: large-scale, dynamic populations of automated trading systems. This paper discusses the possibility of developing a large-scale open, agent based ``economy'' to act as a challenging test environment for electronic commerce solutions based on agent technology. Such an environment would allow researchers and developers to better understand the properties and characteristics of their systems whilst stopping short of deploying them in a real-economic environment. Although we describe some preliminary work in the context of the Agentcities initiative we intend this paper primarily as fuel for discussion.