I am successfully mean all the time. When goals are things like, "I want that person to stop talking and go away," mean works wonders. This isn't even like ciphergoth's "Do a mean thing nicely." I mean blatant, over-the-top sarcasm and public status attacks.

Of course, the best of all worlds is to be mean to your target while appearing nice to the environment. It is sort of like lying with factual truths.

EDIT: Oops, I forgot the actual point. There are times when I stop and think, "I will be nice this time and try more tact." Later, after a night of tiptoeing around the fool, I realize that I should have just been mean.