I totally agree with our learned friend, Mr. Fry.
Having spent years loitering around comedy clubs and the suchlike, it's clear to me that swearing is simply a tool that one can choose to use when apppropriate. As others have mentioned on the thread, acts such as George Carlin and others such as Bill Hicks, Denis Leary etc have built acts (and entire careers!) around swearing.
Now, the question is - is it appropriate to swear during a magic act. And, of course, the only possible answer here is "it depends". It depends on the venue, the audience and, most importantly, your act. If your act is aimed towards families on holiday/end of the pier/summer season, etc then clearly it would not be appropriate. However, as a comedy magician, I find swearing to be a very useful tool - perhaps not during the 'magic' portion of my act but certainly during the comedic monologues that I use.
To see posts stating that "Only low class people would dream of doing such a thing" I think simply serves only to unfairly pigeonhole performers. Magic IS an artform but art comes in many, many different guises - I would put it to you that by performing in 'non-traditional' venues (such as dingy dive clubs - Lord knows I've been in more than a few!) we are actually spreading the artform to those who may not otherwise have been exposed to it. And also, while we're here - I'm not sure it does to be too precious about any type of artform. Just look at the Punk Rock movement - whether you cared for the music is not the point. It gave the music business the biggest kick up the backside in history and the fallout is still being felt today. I'm not sure it would have been in anyone's best interest to have spent the last 30+ years listening to nothing but Emerson, Lake and Palmer and bloated prog rock.

Penn & Teller do a similar thing in magic. Yes, they expose some secrets but when they do, the secrets are usually more interesting than the trick itself - how often can we really say that?? And I bet they've convinced more than a few youngsters (who like their 'edgy' swearing stylings) to pick up a few tricks to try for themselves. For me, it's all about spreading the artform - I love it when people tell me "I don't really like magic" and then, a few minutes later, they're almost begging to tell them how I could have possibily known the name of the actor they were merely thinking of.
To close, I should say that one person convinced me to buy my first trick and, therefore, changed the course of my life completely. He was working in International Magic in London and his name was Jerry Sadowitz. The funniest, filthiest performer I have ever seen.
And one heck of a magician to boot.
cheers,
Sean