Meh, seeing another one of the people said "I could care less" on 4chan today caused me to rage a little, and decided to take the time to make this post on Newgrounds, since I care so much about educating.
As you see, in the chart that I took a bit of time looking(so I don't have to make my own, for you see I am very lazy):
"if one cares to any degree at all, it is possible to care less, those who care a great deal could also care less."
So, you would most likely want to say "I couldn't care less" in a situation where you don't care about the said subject, rather than saying "I could care less".
Good day.