Notice that in the "care less" example, it is the phrase that has changed, whilst the surrounding language has remained the same, whilst in the "board" example

Notice that in the "care less" example, it is the phrase that has changed, whilst the surrounding language has remained the same, whilst in the "board" example the phrase has remained the same, whilst the surrounding language has changed. I used room and board for the sake of argument because I felt it was easy to understand. It may be true that the meaning of could care less has changed, but Pinker’s analysis is that it has not — it always meant the opposite of its literal interpretation. You really can’t imagine some kid intoning in a sickly sarcastic voice to their parents, ‘Oh, I could SO care less!’? You must realize the kind of massive influence youth subcultures have on the language, and from there it’s really not a big leap to image how a usage could enter the language that means the opposite of its literal interpretation. "Room and board" is not in popular usage whilst "I could care less" is (as far as I understand). Thus the potential for confusion is greater. Completely disagree. A quick look at the number of hits in Google’s index shows that they’re both in common use: 2,220,000 for "could care less” 1,960,000 for "room and board" Anecdotal, but telling. If you really wanted me to, I could do a corpus search in the Corpus of Contemporary American English, but I expect the results would be about the same. "Room and board" has a long established use. The use of "could care less" is much more recent. I checked the OED and could care less seems to have been in use since the 1960s. Therefore, both phrases have been in use since well before I was born. So, for me, and most people who aren’t really old, they’re both completely established. If you found the phrase confused you, I'd comply. The crux, though, is that it would still be in the language. Just because you stop producing it doesn’t mean it’s been wiped from existence. If someone came up to you and used it, you couldn’t help but understand what they just said to you. More importantly, though, there’s no reason why you should stop using perfectly legitimate language just because someone else says it doesn’t make sense, but when it’s obvious that it does make sense, because everyone understands you when you say it.