Taking issue with some aspects of the methodology of "critical discourse analysis", as exemplified in the work of Norman Fairclough, Teun Van Dijk, and Ruth Wodak, this paper seeks to show the value of exploring empirically both the encoding and the decoding discourse practices that mediate between media texts and sociocultural practices, an approach that it names as a holistic "discourse ethnography". The value of such an approach is that it can contribute in a genuinely critical manner to the debates about contemporary media culture. Focusing on a "responsibility ad" from the oil company BP, the paper's analytic method combines a careful attention to textual detail with systematic fieldwork that explores the meaning processes of text producers and recipients. In other words, it considers the whole communicative circuit of BP's "responsibility ad", including its textual features, the purposes of its senders, and the meanings generated by its recipients, using empirical ethnographic research. It concludes by turning to the work of the German sociologist Jürgen Habermas on democracy and the public sphere in order to theorize how public companies engage with "the politicization of market discourse".