Our empiral study of the crowdfunding platform Ulule brings out the existence of a cross-projects social network at the platform scale. This social network has a catalyzing effect on the crowdfunding campaigns. The results highlight five sub-groups of contributors within the social network – sponsors, followers, precursors, specialists and collaborative specialists. Then, the analysis underlines a global and positive impact of the social network on the success rate. This positive influence becomes even more significant in the presence of sub-groups of contributors characterized by some thematic specialization and higher rates of collaboration.