I always saw "I could care less" as a way to say you've got a tiny bit of interest in something but you aren't really committed to a solid opinion on it. Example: "What do you think of chopping down the rainforest?" "Eh, I suppose I could care less." Of course there are times when it's said with a tone that clearly means "I couldn't care less."

Honestly, most of the phrases that stick out at me I say myself, so I keep my mouth shut on this sort of thing.