A good friend of mine is wont to exclaim, "I could care less what she thinks."
And that's fine, but by saying that he "could care less," he actually is saying sure, he could care less if he wanted to, but he doesn't want to. Right now he just wants to care a little.
I think what he really means, though, is that it's just not possible for him to care less than he does now. So he should say, "I couldn't care less what she thinks."
That's far more accurate, don't you think?