Network Function Virtualization (NFV) and Software Defined Networking (SDN) are key technology enablers for cost reductions and new business models in networking. The possibility to automatically and dynamically scale network services at run time is one of the main claims of NFV. Elastic NFV could be similar to what elastic cloud services provide for compute, with pay-per-use cost models for customers. However, control of resources for elastic services is far from trivial. We show how current NFV and SDN architectures could support elastic resource services for Network Functions (NFs).