In reputation-based peer-to-peer systems, reputation is used to build trust between peers and help selecting the right peers to download from. In this paper, we argue that reputation should not be used for service differentiation among the peers. To provide the right incentives for peers to share files and contribute to the system, the new concept of
is introduced for partially decentralized peer-to-peer systems. Service differentiation is achieved based on the
of the peers rather than their reputations. Simulation results assess the ability of the proposed algorithm to effectively identify free riders and malicious peers that upload malicious content, hence reducing the level of service provided to these peers and preserving network resources. On the other hand, good peers that contribute to the system receive better services which increases their satisfaction significantly.