Interesting thread. Seems to me one that is woven into screwups leading to headlines in other places beside the antipodes....
For example, Colgan.
Looking at it from the perspective of a gliding instructor for 25 years, (also PPL/IR etc etc) I have found that some wouldbe pilots suffer from a shortage of brain. Especially when tired, challenged, scared. If you have two people with these defects in one cockpit, all the pax in the back can do is hope the laws of luck will spare us.
Question is how to identify them and suggest they take up a less exciting career....