Good question that goes to the heart of the matter. Two answers, I think.
First answer, which applies to broadcasts (without distinction over here between methods of delivery), is that it depends on the time of day/kind of audience you're aiming for. There's a general consensus that you don't use swear words on kids' programmes, for example. Other situations are less clear but, generally, 9pm is regarded as a watershed time.
Second answer is a linguistic answer. Those words exist for good reasons. Is it linguistically appropriate to use a swear word in the context? Olberman's cop-out is a good example in which it was linguistically appropriate - in point of fact, necessary - to say fuck rather than hell. At the other extreme, gratuitously peppering one's speech with swear words tends to diminish their linguistic importance. That's a bad thing, I think. And in between those extremes there are all sorts of in between states that are very difficult to make rules about. Which is why I'd oppose rules and, in fact, the entire concept of "who decides".
MG