"I could care less" is generally understood to be ironic.
No, it's not.
Unless by "ironic" you mean "a word used to cover the fact that I'm ignorant of correct usage" then yes, sure, it's used ironically. 
Granted. "Sarcastic" would have applied better there. It's still early in the morning and I didn't think that one throgh. One bit of pedantry at a time, though. :^)
I suspect you're trying to think the best of people there, it's admirable I suppose, but sometimes people genuinely are ignorant, it's perfectly fine to recognize that.
I don't think it's reaching too far to say that most people, when looking at the words, "I could care less." would recognize that some degree of caring would have to exist for that to be true. It's right there in the phrase. People know what words mean. They aren't often experts at USING them, but it only takes a moment of thought to interpret that phrase. Of course, it's also an idiom, so it often gets used without any thought at all, like I said originally. To me, though, pointing out the meaning of "I could care less" is like telling someone that, no, cats and dogs aren't falling out of the sky outside. You know what they meant, they know what they meant. Very little caring has happened on their part. Communication: successful.
Here's an interesting write-up that suggests that maybe it started as a bit of yiddish sarcasm:
http://www.worldwidewords.org/qa/qa-ico1.htmEDIT TO ADD: And after posting that I look at the responses to this:
http://answers.yahoo.com/question/index?qid=20121008163558AAF1Jny and wonder if maybe people DON'T all know what words mean...