Originally posted on 05/20/2014:
Both phrases are actually widely acceptable, conveying the same meaning through two different language mechanisms...but many who need to feel smarter than they are make a point of correcting what they perceive to be the wrong use. Even if you ignore the fact that sayings like this don't usually make logical sense in a language, "I could/couldn't care less" are similar to other equally acceptable phrases; for example, both "Bobby knows shit about playing poker" and "Bobby doesn't know shit about playing poker" are accurate