The rapid development of Internet applications and devices has greatly reduced the costs of coordinating and participating in many social and cultural activities. Over the last 15 years or so, there has emerged, through both corporate or individual initiatives, numerous large collectives producing information available to all. Beyond the paradigmatic example of Wikipedia, online video platforms, blog networks, and consumer reviews sites have together built rich data resources, based on free contributions and organized by site administrators and algorithms. These web-based platforms gather heterogeneous contributions from users, which are reconfigured through the operations of selection and aggregation, then sorted and shaped in order to make it meaningful information for their audience. Several terms have been used to describe this mechanism: “collective intelligence” (Surowiecki 2005), “wealth of networks” (Benkler 2006), and “wikinomics” (Tapscott and Williams 2005). The analyses of these authors highlight the ability of such forums to create greater value from scattered individual contributions. They emphasize the efficiency of algorithms and the coordination of technical systems that enable the aggregation of subjective and local contributions into a larger whole that is relevant for users. Overall, these systems and the mathematical formulas that support them, whether simple or complex (based on rankings, averages, recommendations, etc.), are able to build valuable assets from myriad heterogeneous elements produced. [Introduction de l'article]