The discussion continues in comments here and at Caleb's. For whatever reason, it has reminded me of the following quote from Jim Cirillo's book, Guns, Bullets, And Gunfights: Lessons And Tales From A Modern-Day Gunfighter:
1. Are you a competitive shooter?
2. Have you competed in major matches and won awards?
3. Can you perform well under pressure or fear?
4. Are you a hunter? Have you shot big game?
5. Do you like outdoor physical sports?
6. Do you collect firearms? Do you reload ammo?
7. If you are over 28, are you married? Do you have children?
8. Do you like people? Do you attend civic affairs?
If you can answer “yes” to at least seven of these questions, you can make it. If you make all twelve, you will likely walk away from almost any armed confrontation.
Remember one important fact: even if you do fit the above profile in all aspects, you still must be able to train at least two hours per week, with someone else administering unknown judgment firearms courses under time limits and psychological pressure.
-Jim Cirillo; Guns, Bullets, and Gunfights, pp. 59-60.