My best friend (who is now in her first year of NYU med school) was also never invited to interview. We too had heard that Columbia always interviews their undergrads, so she was feeling pretty ****ty, and was sending them letters about how much she likes the school, and calling to see if her app was complete. Still...she was never invited, and ultimately rejected. So I don't know why they didn't invite her... but yeah, I heard the thing about "curtesy" interviews for Columbia undergrads...