As new network services emerge, questions about service deployment and network choices arise. Although shared networks, such as the Internet, offer many advantages, combining heterogeneous services on the same network need not be the right answer as it comes at the cost of increased complexity. Moreover, deploying new services on dedicated networks is becoming increasingly viable, thanks to virtualization technologies. In this work, we introduce an analytical framework that gives Internet Service Providers the ability to explore the trade-offs between shared and dedicated network infrastructures. The framework accounts for factors such as the presence of demand uncertainty for new services, (dis)economies of scope in deployment and operational costs, and the extent to which new technologies allow dynamic (re)provisioning of resources in response to excess demands. The main contribution is the identification and quantification of dynamic (re)provisioning as a key factor in determining the preferred network infrastructure, i.e. shared or dedicated.