^ I agree with you there, I think no matter how much you censor yourself (or just don't use four-letter words because you don't like them), the kids will pick them up from somewhere and it's just part of life - like them going through the phase where they're obsessed with bums, bodily functions and genitals... it's not 'polite' but it's a novelty and the less of a big deal you make of it, the more likely they are to grow out of it, kwim??
I just worry because I'm not the most conventional-looking mother (lol I get the weirdest looks when I'm out doing the groceries, especially in a small town) and I know people judge me enough without having the old, 'You're a horrible parent for allowing your child to swear, especially because *your* child has taught *my* child how to swear' thrown into it!!
Not that I think kids learn swear words from just one other kid, I know when I was young my parents used them, I heard them on TV or in movies my parents watched, and *everybody* at school used them on the playground - it was pointless trying to blame Jane Taylor or Caleb Jones for 'teaching' me because we all knew them!!