Jan Freeman, "I could care less: A loathed phrase turns 50", The Boston Globe, 10/24/2010:
It was 50 years ago this month — Oct. 20, 1960 — that one of America’s favorite language disputes showed up in print, in the form of a letter to Ann Landers. A reader wanted Ann to settle a dispute with his girlfriend: “You know that common expression: ‘I couldn’t care less,’ ” he wrote. “Well, she says it’s ‘I COULD care less.’
Ann voted with her reader — “the expression as I understand it is ‘I couldn’t care less’ ” — but she thought the question was trivial. “To be honest,” she concluded, “this is a waste of valuable newspaper space and I couldn’t care less.”
She couldn’t have known it at the time, but her reader’s trivial question would be wasting newspaper space (and bandwidth, too) for decades, as it blossomed into one of the great language peeves of our time.
An on-going discussion on metafilter has a remarkable heat/light ratio, amply supporting Jan's point.