Apart from the existing media (press, radio, television), the on-line news sector involves several categories of actors. One of them, the infomediaries, is in a central position, half-way between editing and publishing. The socio-economic analysis of this category in three case studies (Google News, Wikio, and Paperblog) reveals its pivotal function in the orientation of audience flows and advertising income. In a situation of 'coopetition'? with professional publishers, the infomediaries do not participate directly in the financing of journalistic creation. More generally, their relations with the producers of content influence the type of news - professional or amateur, dominant or alternative - made available to internet users.