I've heard this all over the place: "I could care less". What does the person usually mean when he/she says this? That they don't care, of course.
But think about it for just a minute: If you could care less, that means you must care something about it already. I believe that this mis-quoted phrase probably stems from the more correct "I couldn't care less", and people just dropped the n't without thinking about how they were significantly changing its meaning.
I had a co-worker named Kevin several years back who told me that people, in general, don't like to think. This is just one small piece of evidence in support of this claim.
If you have used this phrase, consider thinking about what you say a bit more, please. Let's keep the english language a little less confusing to those learning it. :)