Web 2.0 services allow large amount of users to interact and share resources with each others in a very easy and timely way. However, as such services are very recent, there is still a need for developing new tools that considers their own characteristics and particularities. This is the case of the resource access control methods. In this paper we present the Max-Min method, a new trustbased algorithm for computing user reputation in social/peerto- peer networks in an easy, fast and comprehensible manner. For these reasons, it can be used for resource access control enforcement. The novelty of Max-Min is that it is specifically designed for Web 2.0 applications. Therefore, it considers all the particularities of such scenarios. Additionally, we nclude in this work a set of experiments showing the viability of Max-Min model using a real trust dataset downloaded from Epinions, a Web 2.0 website.