In this paper, we explore a quantitative approach to accountable networked systems. We propose P-Accountability, a novel concept and general metric, to assess the degree of system accountability. As a preliminary case study, we apply P-Accountability to PeerReview , an accountable distributed system. A quantitative relation between P-Accountability and message loss probability is given. We re-evaluate PeerReview with the notion of P-Accountability; the results show that network dynamics will affect P-Accountability and that PeerReview is not able to achieve perfect accountability in a realistic network when message loss is not avoidable. The purpose of this paper is to present early research results in the particularly interesting and innovative field of P-accountability research.