Trim Stab,
It's a great question. The commenters who suggest that insecurity is a great motivator
know nothing about human factors, good management practises or what it is to feel insecure.
For the serious people, there is only anecdotal and subjective commentary on the subject. The reason: the age old problem of measurement.
How do you measure employment insecurity? How do you measure the different reactions between human beings to employment insecurity? How do you measure the correlation between the reactions of human beings generally and operational performance? How do you measure the correlation between the operational performance of individuals and the safety of a flight? How do you measure aviation safety?
Tough subject for objective research....