I use it alot, but normally not directed at someone. Might be an odd time where I might say, "Damn you pirates!", but thats in role-play. If anyone is going to take a screenshot, of you, saying damn, and then reporting you for using foul language in a non-RP way, that very fine line that says "this is a game", gets crossed and no longer becomes a game for having fun... :D
And once that line is cross, you'l find that no matter what you say, you may never be SAFE!:P
I've ahd some rather fruitful chats in my time, words like Dam,Bugger,Darn,scum, hell,fool, to some point Biatch (not to sure on that one) but hey i'm one of those people who scream at the screen and not on the key board. Or if you have the person on Xfire or Skype or whatever you use say it in there.