Long before having kids, I was known for having a potty mouth. I'm not sure why (OK, I guess I know why), but I developed a reputation for it among friends. This was never a big deal to me until, of course, I had kids. Turns out, cursing in front of your kids is not generally smiled upon, so I found myself desperately trying to edit what came out of my mouth and with varying degrees of success.
Personally, I hobble back and forth between caring and not caring if and when my kids hear me swear. I tend to use certain curse words as a means of letting out anger and frustration, and it's generally not directed at people. In this regard, it doesn't seem like a terrible thing, relatively speaking. If I were walking around calling horrible names that are meant to degrade them or hurt them in some way, I could see being criticized for doing so in front of my kids (or, you know, at all). I don't want my kids to learn that calling people names is acceptable, but using a swear word to express frustration? That doesn't bother me, really.
The problem, of course, is caring about what other people think. If we lived in a bubble, where no one's opinion mattered (meaning, your kid's teacher or family members or other mom friends or strangers at the park within hearing distance), I wouldn't think twice about my kids learning a few swear words. But judgment is everywhere so, for now, I'm trying to keep it to a minimum at my house. That's why, of course, I am usually bombarded with some variety of these 10 thoughts I'm sure most moms have when they accidentally f*cking curse in front of their kids: