I don't know that I've ever seen a feature that wasn't some sort of "failed promise". The feature sometimes hits and sometimes misses, and is usually somewhere

I don't know that I've ever seen a feature that wasn't some sort of "failed promise". The feature sometimes hits and sometimes misses, and is usually somewhere in between. This idea that a defect is a failure of a feature is probably more to do with the inability to predict the future. Sure there are defects like you tried to read from /dev/null, but more realistically the "defects" you see today are more about the inability to predict exactly how a feature is going to be used.