Swearing is a great way to let people know what kind of person you are.
I always try to get in a few quiet 'fucks' into the conversation to get a guage of the type of person I'm talking to (using less harsh words as the situation dictates).
I also laugh inside when ever I say 'cheers' (by way of 'thank you') but replace 'cheers' with 'jizz' (it sounds almost exactly the same with my accent). Hilarious!
Some times the right (wrong?) swear word in a conversation can be equally hilarious. If someone was to pull me up on swearing in normal social conversation I could conclude that they don't find the same kind of things funny as I do.
My friends and I often make up bizarre novel swear words and text each other just to see who can create funniest words; great fun.
Swearing for fun is ace: using swear words for evil is as bad as using any words for evil.