Folksonomies are a new model for structuring data on the Web, based on the free indexing of keywords by Internauts. They provide new media for existing forms of social navigation. This article draws on a series of interviews with users of the Flickr site, to propose a typology of uses of tagging systems. Although it seems to be an individual practice, this categorization prompts users to enter into multiple forms of cooperation, ranging from implicit cooperation - made possible by the aggregation of metadata by the system - to more coordinated forms of cooperation within user collectives.