[SamAdams76]

What annoys me is when people say "I could care less" when they actually probably mean "I couldn't care less."

So when they say the former, I usually say "So you care at least a little?"

[Genoa]

Yeah, so don’t I.

[TalBlack]

You’re hearing it without the rising inflection and the emphasis on the “I”. It is a question delivered with an air of irony. I can remember some old Jews using it this way when I was a kid. You will see it in old movies from time to tim. Old books as well.

[ican'tbelieveit]

irregardless.

[elcid1970]

See Weird Al’s “Word Crimes” for caring less.

:^)

[wideminded]

What annoys me is when people say "I could care less" when they actually probably mean "I couldn't care less."

I think that one is an American idiom, so it's not exactly the same class as other grammatical errors. Most Americans know what it really means. Even people who have otherwise perfect grammar might occasionally use it. Using this expression accentuates the idea of how little you care because you are not even caring enough to have perfect grammar. So it is a little bit clever in that way and sort of likable that it is a peculiarly American expression.