In this article the authors first briefly present the Portuguese blogosphere and the place within it of blogs specialized in media critique. They then consider the two underlying reasons for the success of these blogs - beyond the relevance of the Habermasian model of the reconstruction of the public sphere in a post-totalitarian society. The first is the insufficient collective reflexivity of press firms in Portugal. The second reason is the specific socio-professional profile of the hosts of these sites with a reflexive purpose. The hosts of the blogs studied reinvent the model of press opinion on the fringes of journalism and become actors in their own right in the construction of news in Portugal. In so doing they play a significant part in the external critique of the Portuguese media system and in the expansion of a public space that is still strongly constrained.