The literature on platforms emphasizes the balance between supply and demand as precursors to network expansion, strategy development and strategy sustainability. This study questions this logic through the exploratory approach of a public platform based on social returns. Results demonstrate that when an institutional force supports a platform concerned with diffuse and collective interests, it is possible that the strategy could sustain and develop without the balance of its forces. The study contributes to the strategic platform literature by pointing out the distinct aspects of social platforms and underlining the support generated by institutions.