This - As an interviewer I hate giving feedback on failed interviewees. It always feels like an insult as well as invitation for them to defend themselves after the decision has been made (which means I have to say no again, doubling my unhappiness and presumably theirs.

As an interviewEE , though, feedback is essential to improving and definitely reduces the sting of a failed interview. (My sample size of both sucesses and failures is small but feels huge anyway).