I swear, but never around my kids. Moved to a new town late last year and I joke not, the kids on my street are tossing around the f-word like it's nothing. When I say kids, I mean children as young as 5. I caught one of them teaching my son how and when to say it, and put the fear of God in them accordingly. Funny how I'm now the only mom on the street the neighborhood kids respect. My son said it ONCE in my presence. Pretty sure it's the last time he'll make that mistake.
My goal is to raise a much smarter, polite and respectful person than I am. So far so good.