I find though, that swearing can be overused in fiction, especially movies and television. Take the show Deadwood as an example. When this show was being created, it was decided that period-appropriate swearing sounded a bit silly by today's standards. That's fair enough, modern audiences need to find something they can relate to in a story to feel connected.
But in the first scene alone, the amount of repetitive swearing takes over and it feels like dialogue has been replaced with swear words. This doesn't feel intimidating or edgy, it feels lazy.
Take another HBO series, Rome as a different example. The writers used a variety of modern swear words and slurs, but in a very measured way. The menace and intensity of the characters comes across in smooth dialogue and sharp delivery. Sticking with westerns, watch Unforgiven and see if the lack of frequent swearing makes Gene Hackman or Clint Eastwood any less intimidating.
We have a beautiful, diverse language available to us. Why rely on quick fix words to get a brief reaction when you can take the time to build real tension and fear between your characters?