This presentation provides a brief overview of the FP7 Network of Excellence (NoE) Peer-to-Peer Tagged Media (PetaMedia). This NoE has been established and conducted with the goal to explore the possibilities for developing advanced solutions for multimedia information retrieval (MIR) in the social network context. PetaMedia has approached the realization of these solutions based on the triple-synergy paradigm. This paradigm provides a conceptual framework for MIR that builds on integration of three information sources: multimedia content analysis (MCA) (automatically assigning metadata to multimedia data using signal processing, data mining, computer vision and pattern recognition), user-contributed annotations (e.g. tags, comments, ratings and explicit recommendations), and analysis of social networks (analyzing information flows in networks and deriving implicit relations and preference specifications among users, content and metadata). The presentation illustrates the achievements of PetaMedia using the examples of its MIR soluitons developed on the basis of the triple-synergy paradigm. It also provides an overview of the efforts within PetaMedia that targeted dissemination of these results in the broad MIR research community.