Motivated by the vision of Network Functions Virtualisation (NFV) spanning different administrative domains, this position paper makes the case for multi-domain, distributed NFV (MD2-NFV). To this end, we present MD2-NFV as a natural evolution of the NFV paradigm to deliver a distributed deployment of Virtualized Network Functions (VNFs) as a service. By means of three motivating use case scenarios, we discuss potential benefits and identify challenging features towards enabling advanced peering relationships between NFV domains.