Could care less when they should be saying could not care less.
I hope folks who are saying the former are saying it "ironically"
I don't think I've never heard "I could care less" used ironically to imply that the speaker could not care less. I am tempted to suggest that most who say "I could care less" are incapable of detecting irony, to say nothing of employing it, but that would make me a word snob, so I shall say no such thing.