I hardly ever use sarcasm directly towards a person I am talking to (except my husband when I'm really really REALLY mad at him, but that is pretty rare and I don't actually think it's okay even then, I just get carried away). But I think it's okay to make fun of big political figures, people in the news who are acting ridiculous, the Borg. It can establish a common ground with other people. Of course it could also land you in a fistfight pretty fast. I think you do have to walk a fine line with sarcasm, or it can just come off heavy handed. The English are great at it. I'd have some little interaction with a shopkeeper or whatever, and I'd be two blocks away before I'd realise they'd insulted me, and I'd still be laughing even though it hurt because they were just so dry and subtle.