Silly phrase.
See, in other parts of the world, you say "I couldn't care less", meaning that you care so little about said topic that it would be impossible for you to care even less about it. Saying that you could care less means that you must care to some degree, because it would be possible for you to care less than you currently do, and your current level of caring is not the minimum possible.
Yes, I know I'm drunk, but that doesn't stop me being right.
*razz*
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