  Web 2.0 works with the principle of weak cooperation, where a huge amount of
individual contributions build solid and structured sources of data. In this
paper, we detail the main properties of this weak cooperation by illustrating
them on the photo publication website Flickr, showing the variety of uses
producing a rich content and the various procedures devised by Flickr users
themselves to select quality. We underlined the interaction between small and
heavy users as a specific form of collective production in large social
networks communities. We also give the main statistics on the (5M-users,
150M-photos) data basis we worked on for this study, collected from Flickr
website using the public API.
