A Slashcode-based discussion forum might be a good way to model the kind of critique we'd like to foster on the site while also encouraging discussion. The moderator who posts can include a news brief ("Pepsi will increase urinal advertising in schools") and make some comments about what the implications are and
Note I say this *might* model critique. In casually trying to maintain critical discussions which have arisen on my website, I've found this extremely difficult. The main issue is that people find the site through search engines and ignore the post which begins the discussion, jumping in at later parts of the discussion where visitors have veered off and begun to chat about the ways in which they enjoy a particular media phenomenon.
Threaded posts and possibly some kind of bot-protection (which allows search engines' site-finding bots to view and archive only the main post, for example) might ameliorate this problem. Heavy participation by youth moderators who are invested in media critique or by hired goons ^H^H^H^H^H^H moderators might also help.