Emergence of P2P systems had an unquestionable impact on data and media interchange over the Internet, to the point of seriously challenging traditional actors of the music business field. Technical issues concerning the deployment of P2P networks are more or less well described; they rely on well-known transmission protocols and benefit from the mass-effect of Internet. But for the moment, the question of business viability of P2P chains of media diffusion is still open. This paper proposes a model to better understand and compare the different actors confronted to or exploiting this important technological change. The final objective of this model is to provide a better characterization of each actor's abilities, along with the impact of new technological opportunities (like P2P systems) on their respective activities. The proposed model is directly derived from the e-business model ontology developed by Osterwalder & Pigneur for characterization of value-chains in e-Business fields.