Some of the most noteworthy developments in communication behaviours (open-source software, Wikipedia, P2P, blogs, etc.) have not been initiated 'from above', via an industrial development plan and the launching of a new technology invented in a research laboratory; rather, they have taken shape 'from below', through a cooperative process involving networks of users participating on a voluntary basis. This type of 'horizontal' dynamic, which develops independently of the 'vertical' cycles of innovation, was an essential if not exclusive characteristic of the development of the first age of Internet, its use and its market. In the bottom-up innovation processes, three distinct circles of actors can be distinguished: the core innovators, the network of contributors, and the circle of reformers. Using different examples of recent bottom-up innovations (Wikipédia, alternative metrics, etc.) we will try to give sociological characterization of the sociotechnical trajectory of those innovations. With the massification of uses and the rise of hegemonic platforms (Google, Facebook, Amazon, etc.) the role of bottom-up innovation in the digital economy seems to have vanished. We’ll try to explore how the asymmetrical relationship between web platforms and internet users creates a new context for horizontal innovations.