I interviewed with a Columbia alum today. It was a casual setting and lasted about 70 minutes. Main discussion points were-
1. My extra curricular work (volunteering - why I chose to do that, what I did/achieved....)
2. My future goals, short and long and Why Columbia MBA
3. Couple of leadership stories from my professional work that were mentioned in the resume
We did not discuss ethical dilemma, failure, weakness etc. Instead we spent more time digging deep into the 3 points mentioned above. I think it's good to prepare for these kind of broad topics but also make sure you can substantiate your stories and go into more details if need be. Being confident and knowing my stories very well helped me to discuss finer details. I think I did well, hope and pray I get the admit

Fingers crossed.