I, myself, tend to be overly formal with people at times; but once I am familiar and comfortable enough to stop using the 19th century etiquette I learned as a child and start using Pickwickian ribbing, I know that a person is actually my friend. Still, even amongst those who are very much my friends, there are some I'm more likely to use that style with than others.

Oddity: I don't call female friends bitch. I will call male friends bitch, and anyone of any gender ass, and jokes about what so and so did with such and such's mom and the infamous Saint jokes about "what happened to your face? I forgot, you were born like that" are thrown about with wild abandon, but I don't like to call girls bitches unless I really actually mean that they are bitches.