"could care less" is actually wrong -- it literally means that you do actually care about the thing in question.
They could care less if it's wrong ;p
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."
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..."