to as the "freeloader problem"). Freeloading can have a profound impact on the network and in some cases can cause the community to collapse. [ 43 ] In these types of networks “users have natural disincentives to cooperate because cooperation consumes their own resources and may degrade their own performance.” [ 44 ] Studying the social attributes of P2P networks is challenging due to large populations of turnover, asymmetry of interest and zero-cost identity. [ 44 ] A variety of incentive mechanisms have been implemented to encourage or even force nodes to contribute resources. [ 45 ] Some researchers have explored the benefits of enabling virtual communities to self-organize and introduce incentives for resource sharing and cooperation, arguing that the social aspect missing from today's P2P systems should be seen both as a goal and a means for self-organized virtual communities to be built and fostered. [ 46 ] Ongoing research efforts for designing effective incentive mechanisms in P2P systems, based on principles from game theory, are beginning to take on a more psychological and information-processing direction. Although peer-to-peer networks can be used for legitimate purposes, rights holders have targeted peer-to-peer over the involvement with sharing copyrighted material. Peer-to-peer networking involves data transfer from one user to another without using an intermediate server. Companies developing P2P applications have been involved in numerous legal cases, primarily in the United States, primarily over issues surrounding copyright law. [ 11 ] Two major cases are Grokster vs RIAA and MGM Studios, Inc. v.