This is not coming from a politically correct standpoint. I have been known to swear like a trooper on more than one occasion. (Okay more often than that). Much to the dismay of my mother.
I guess it just happens that a recent heroine has brought this to the forefront of my mind. And I'm not referring to when it's being used in a sexual context but in general day to day conversation.
I have come to two conclusions.
1) When it comes to swearing less is definitely more.
2) Swearing is not an effective replacement for character development. Just because the heroine can say fuck three times in the same sentence does not make me believe that she's a tough cookie. It just shows me that she can say fuck three times in the same sentence. And no, I'm not particularly impressed that she can use it as a verb, adjective and noun.
Some of the toughest heroines I've read - Elena Danvers, Nadia Stafford, Phaedre, Kate Daniels, Mercedes Thompson - did not have to constantly say fuck to get people to take them seriously.