From my understanding, many times bad things have been prevented just by the sight of a firearm or the person intending to do harm knowing there is a firearm present. 1911A1 Fan didn't have to draw his weapon, he just had to imply he was ready and willing to use it and he was prepared at that moment to do so.
My best friend's dad is a police rangemaster. He is a big time runner for being 50 years old and he runs in the rural areas near a big city all of the time. One early morning, he was getting out of his truck to go run when he saw two gang bangers drive by real slow. He was thinking of going elsewhere when he said screw it, they aren't running me away. So he goes on his jog. Sure enough, on down the road there is that car on the side of the road and the gangbanger types are out of the car. One of them starts to approach the off-duty officer and the other is starting to move around to flank him. As the gangster approaches my friend's dad he says, "I think we have a problem." My friend's dad replies by unhosltering his Glock 27 half way out of his fanny pack, no words, just showing his Glock. The guy confronting him doesn't act shocked (possibly doped up), he just says, "We have a flat tire." The guy flanking the officer looks pretty shocked and starts back peddling the other way. Officer replies, "So." Gang banger says, "Do you have a cell phone." Reply, "No". The two gang bangers get back in the car and drive away. The picked the wrong guy to try to rob that day, it is a good thing for them they decided to leave him alone as I know he would have humanely dispatched them post haste.
Lets all remember this as we carry. Often all we have to do is let on we are not going to be easy pray, and that is enough for a self-interested criminal to go else where.