Mobile ad-hoc networks (Manet) and peer-to-peer (P2P) systems are recently emerged technologies which share a common underlying decentralized networking paradigm. However, the two fields have been mainly investigated by different research communities, without catching several cross-cutting issues. Both systems share some common issues and relevant differences: however, similarities could be exploited in a more synergic way when coupling the two systems. In particular, very recently, some cross-layer approaches have appeared, trying to improve the overall performance of a P2P-Manet system: in this paper, we analyze them in order to identify some common guidelines and the most promising approaches. Indeed, since many combinations of Manet routing algorithm and P2P overlay network building are possible, our analysis also aims to minimize common pitfalls in designing such kind of applications.