I am always find it strange when I hear people say "I could care less". Logically, it means that you are able to care less than you are currently caring about the thing being discussed, which is usually something the person speaking is expressing ambivalence about.
It makes much more sense to say that you are currently caring about this thing the least you possibly can - i.e. you couldn't care any less about it.

So to the people that say "I could care less about..." - well, why don't you?