I try not to swear as a rule, although the occasional descriptive word for dog's muck has slipped out when I get it on the hose.
If I'm in the pub and a workmate were to laughingly say "You daft (insert mild swear word), you!" in a friendly way it wouldn't bother me, but you get some selfish thick so-and-so's who swear every other sentence and I don't count them among my acquaintances.