My DD is 16 and has taken to swearing at us (i.e. telling us to fuck off) whenever we nag her to do something (e.g. turn the music down, keep quiet, your brother is sleeping or pick up your dirty socks) or when we disturb her in her room. This morning, I got it because she told me to wake her up at 9, which I did.
It has become a bit of a habit now and DH, in particular, feels very hurt by it, whereas my tactic has been to ignore it (or say it back if I'm in a particularly bad mood). But even I am finding it a bit much and it's time to try a different tactic.
I think it is partly a generational thing. She has no qualms about using the word, cunt, whereas people my age can't even say it out loud. To DD, it's just a word and, in her words 'not racist or anything', which shows she has some morals.
I definitely feel it is a respect thing. Even her friends pull her up on it sometimes.