My main characters tend to be males aged between 16 and 28 and I almost exclusively write in a contemporary setting. My characters are also usually very passionate people who wear their hearts on their sleeves. One of my characters is also Irish. Therefore, my characters curse. Sometimes, an inordinate amount. Why? Because 20-something males curse. A lot. I actually tone it down from my normal speech patterns. Do I have them f-bombing every page? No. That's not how people talk. People don't swear indiscriminately. They build up filters based on the social situations. At work, instead of yelling out an s-bomb when I stub my toe at work or drop something, I yell out "Crap!" But if I'm home alone and I drop something, I will spew forth a string of curses which would make a sailor blush.
In my opinion, I feel that you should write for your audience and write for your characters. Would Michael swear? Probably not. Would Harry? Probably. Would one of Marcone's low-level thugs? Probably every third word. The Dresden Files isn't meant for children. Dancing around cursing by characters would feel awkward in the prose. If you're writing something for young adults or children, then of course you should cut out the cursing.
Here's the big thing, though...many people are offended by certain words. For some people, it's the f-word. For most women, it's the c-word. However, you have to balance in your mind alienating some of your audience by using these words and how much the prose suffers from losing them.
In my opinion, the worst thing you can do break the fourth wall by using fake curse words unless it's something your character would do. If you watch the TV show Scrubs, it's part of the character of Elliot that she doesn't swear and says words like "frick!" when she would normally curse. However, if you use "friggin'", "freakin'", "crap", "heck", etc. too much without a good reason, it will seriously damage the flow of the narrative because it makes me think about the author's motivation. This is really bad in sci-fi and fantasy because authors in these genres have a bad habit of making up curse words. I love Battlestar Galactica, but I'm SO sick of "frak". Shadowrun finally ditched "drek" and "frag". Red Dwarf is at least creative about replacing curses, but "smeg" became comedic after a while.
Just like the choice of how graphic your violence should be and how much detail you should use in describing sex, you have to think about your audience and the style you're going for. The prose should come first above anything else. Don't censor yourself at the expense of your story and your style.
The Abstruse One
Darryl Mott Jr.