[apohn]

If I'm the interviewer and an interview has clearly gone badly and both sides known it, I usually just ask the person about something they are working on at work/personally/coursework, or whatever. People are usually happy to focus on something they can talk about and my goal is to end the conversation on a positive note. So if they feel they were able to talk about their project(s) and present their strengths, they can walk away with a more positive feeling.

I think the only exception is if the person has clearly lied about everything on their resume. I don't mean people who have stretched the truth - I really mean the type of person who insists they "I did X" but they clearly did not. I'll just end the meeting early and that's the end of it.

As an interviewee I think it really depends on the situation. If the company and job seem interesting, I definitely try to ask questions to learn more about what they are really doing in their jobs. If the person who interviewed me is an a-hole or clearly not engaged in the interview I just say thanks and end the call.