I've been in the IM field for roughly about a decade now, and I've noticed that it's not uncommon for Internet Marketers to swear in their sales copy. But of course there are many who don't. Some consider it unprofessional and potentially offensive and therefore harmful to sales; others feel it comes across as passionate and daring, and therefore good for sales.
My personal feeling is that it really depends on the audience you're targeting - as with most things. But I think in the bigger picture, it would be better not to do it. And of course I'll explain my reasons as this post develops.
Myself, I'm not a "frequent" swearer. If you hear me swear it's usually because I'm irritated or frustrated with something; I only occasionally swear in casual conversation. Is it because I'm uptight or some kind of prude? I don't think so. I think it's more of the image that comes to mind for me when I think of those who swear casually, frequently, loudly, without regard to who's present, etc. I generally think of such a person as one who is something of a "base" person, lacking self-control and consideration of others. I mean no offense to the reader here.
To me it's like smoking. There are two kinds of smokers: ones who are considerate, and try to stay downwind of non-smokers, and those who are inconsiderate, either because it simply hasn't occurred to them that their smoke is offensive to non-smokers,or because they just don't really care.
Although I have that view of people who swear excessively, I'm not offended by swearing. I've read things by marketers who swore but have offered valuable information - and it's really only the valuable information that I care about.
But I'm also very much aware that there are people who are extremely offended by excessive swearing. And I'm not willing to write them off because I would see it, as our IM cliche says, as "leaving money on the table".
I read an article on the subject by a swearing marketer not long ago and he said, one, you cannot please everyone and shouldn't try to. And two, if they're offended by swearing, he said, "I probably don't want them on my list anyway."
That seemed over the top to me. People who don't like swearing are perfectly welcome on my list - particularly if they're buyers. I'm more than happy to oblige them by not swearing. And as for not being able to please everyone - that's true. However you should please as many paying customers (or potential paying customers) as you reasonably can.
My point is that, like it or not, there are people who are offended by swearing. But I've yet to hear of anyone being genuinely offended by the absence of swearing. I'm not saying there are no such people, but I have no doubt they are far more rare a breed than those who dislike swearing.
The most important thing is that you speak naturally. And when you do, people don't tend to notice if you're swearing or not. But I should add this disclaimer: Don't make yourself look dorky by using "substitute expletives". Words like "darn" and "shoot" only draw attention to the fact that you're making it a point not to swear, and therefore your speech doesn't come across as natural.
The use of the expletive adjectives aren't really necessary to natural sounding speech. Whether you say, "This is so f***ing awesome!" or, "This is so darn awesome!" - either can be off-putting, depending on the reader. You can just eliminate the adjective altogether by saying, "This is so awesome!" The latter is unlikely to offend anyone, and still conveys passion and sounds perfectly natural.
Am I saying you won't be successful in IM if you swear? Not at all. I'm just saying that it's my opinion that you could probably do better if you didn't. But it's like grammar. I myself am somewhat of a "grammar nazi". My biggest grammar pet peeve is when people don't know the difference between then and than. I laughed at a post I saw on Facebook where someone wrote, "I'd rather be pissed off then pissed on." What they wrote literally means, "I'd prefer to be really angry and afterwards have someone urinate all over me." They should have used than - not then.
But I'm so bad about my grammar peeves that if I go to a sales page that is full of grammatical errors (particularly if their sales copy says something like, "There's more people making money online now then ever before", I will not buy the product. Because in the back of my mind is a thought that says, "If they couldn't even be bothered to pay five bucks to have someone on Fiverr proofread their sales copy, how good could their product be?" I see it as a cavalier attitude toward quality.
Nevertheless, bad grammar people are successful online left and right. They may not get my business, or the business of those who are as anal about grammar as I am, but they can still make a lot of money. I think of the guy behind theplrstore.com - his is some of the worst writing I've ever read - grammatically speaking. But it hasn't kept him from being successful.
I'm sure I'm likely to get some haters responding to this. People condescending, people telling me how "f***ing stupid" I am, etc. But I'm not thin-skinned. I'm genuinely interested in knowing people's thoughts.