Since 2005, the Internet has given rise to several novel initiatives concerning journalism designated by the generic term "citizen journalism". Underlying a set of heterogeneous systems, a unique principle can be observed: web users, who are not professional journalists, contribute directly to the production of the daily news. These practices raise a series of questions, one of which is the link, in the media and journalism, between professional and amateur practices (pro-am) and which we will examine in this article.