Yet it seems the people who dislike "could care less" are fighting a losing battle. Here's a statistic about the ratio of "could" vs. "couldn't" in the NYT:
----------"couldn't care less"--"could care less"
ratio
1960-1969 ------- 245 ---------- 5 --------- 2.04%
1970-1979 ------- 369 --------- 42 ------- 11.38%
1980-1989 ------- 274 --------- 77 ------- 28.10%
1990-1999 ------- 248 -------- 147 ------- 59.27%
2000-2009 ------- 259 -------- 194 ------- 74.90%
The whole article
here.