Just like the American "could care less" is the same as the British "couldn't care less". Two nations divided by a common language as someone is supposed to have said.
A pissed american will hit you. A pissed englishman will fall over.
Edit : the correct English term is 'pissed off'. As in 'he pissed me off by going to the pub and getting pissed'.
i think the sentiment is, "I care so little that I don't even want to use all the words needed to say how little I care".
They could care less if it's wrong ;p
Bill: "Hey Ted, check out my fancy landing / lead acquisition page for a product that doesn't exist yet".
Ted: "I could care less"
Bill: "Hold up a minute there chief. Are you saying that you do care? I'm so confused..."
I could (exhibit that I) care less (because I do care less than I currently exhibit).
Or, as a matter of giving the benefit of the doubt:
I could (exhibit that I) care less (because I am, through effort, caring more right now than I would naturally).
or
"I could care less" is actually sarcasm which implicates that caring is obviously unlikely.
Both statements display a stronger degree of uncaring than "I couldn't care less" which is actually a pretty boring and to the point statement. Therefore I find "I could care less" to be the clear winner to indicate how little I actually care.
In summary, "I could care less".
or:
"I care very very little right now, but there's nothing holding me back from caring even less than that."
Most recently it showed up in the dialogue for Disney's Tangled and not even in a self-aware way. Ugh.