At Making Contact there's a very interesting discussion going on about whether or not the use of "fuck" is appropriate in the classroom. The original posting was in response to a perceived "political correctness" issue on her campus, and students complaining about a swearing colleague.
Since I've already commented there, I'm not going to repeat all of what I said. But I just have a hard time accepting that there's a pedagogical value to repeatedly using the word "fuck" in class. If it's in the text -- fine. If a student says it in discussion, then you've got "a teachable moment". But it's different if the teacher is just spouting off.
And frankly, I just don't buy it when people say "I can't help it". After all, we all perform different aspects of ourselves to different audiences. Who I am in the classroom is necessarily different than who I am in other contexts. As a teacher of literature, my responsibility is to use language carefully and precisely -- and in such a manner that will help my students think critically about texts and ideas. If they are shocked, offended, laughing nervously, or overly relaxed because they think I'm "cool", their emotions tend to overrun their analysis. I make jokes, speak in slang, do all sorts of things at deliberate moments to wake them up, or to make a point -- but "fuck" is off limits. Partly because I certainly don't want them saying it to me.
Thinking of an example in my own department: I have a "potty-mouthed" colleague who reportedly focuses on scatological examples in a kind of immature way during lectures. I wouldn't know this first-hand, not being a student. What's weird is that he doesn't act that way with his colleagues. Or, not so weird: we're his peers. To perform your outrageousness, your defiance of convention, by swearing or talking about poo in front of a lecture hall, is either an aggressive display of power, or a really immature bid for attention. Not that it can't be both at once.