@10, 11: Sorry, I was probably unclear, so let me re-state before this goes off on the wrong track. You are correct that "couldn't care less" is logical. What happens is some people mis-remember or mishear or reanalyze or whatever that phrase, and what they say is "I could care less" and in fact they mean "I care so little, there is no way on earth I could possibly care less." But when you think about it, that is not the sense that "I could care less" conveys; in fact, some may even call it illogical.
My argument here is that people are mis-hearing the correct "than ever" and use the incorrect "than never." In the same way, some speakers mishear "I couldn't care less" and use instead the incorrect "I could care less", which to them means the same thing. However, both usages are quite established, wrong or not, so in the same way, I would expect to see more examples of both "than ever" as well as "than never."