I believe that if they know there is a person with a gun in the area, they'll think twice about committing a crime in that area- after all, I wouldn't rob a store if I had just seen a person with a gun strolling down the street. The odds of cops getting there in time to foil the robbery aren't great, but the odds of an armed citizen close by hearing commotion and coming to investigate...
This is what nearly got me killed when we got robbed at the fast food place, though. Unbeknownst to anyone else in the store, our assistant manager on shift at the time had a gun with him that night. When he realized that a large man was holding a .44 at my belly as I stood at the register, he got this brilliant idea that he could run from just behind me to the back of the stockroom in the back of the store (about 20 yards?), retrieve his own gun from the bottom of his gym bag and return to the front of the store to fight the two robbers to save the cash for which the store was fully insured--before the bullet from the .44 was fired and blew a hole through my guts with an exit wound the size of a chicken bucket.
I realize that gun ownership and voting are seen as rights and responsibilities. I also realize that there's a large part of the population that just shouldn't be trusted to do either of them. That's not based on race or politics or anything other than sheer lack of common sense.
Oh, and when we called the police after the robbery a car arrived within less than two minutes. They had been in the nearest lane of traffic at a red light right in front of the store while we were being robbed. They had absolutely no idea anything out of the ordinary was happening.
A year before this happened, I was given pepper spray as a birthday gift. During the three months prior to that birthday I had endured two muggings and two attempted rapes while walking to my home off campus. For years I would not walk alone or in a suspect situation without that canister in hand, safety off, and I asked a Syracuse police officer just where I stood legally. He said that while I was technically carrying a concealed weapon without a permit, anyone on whom I was likely to use it wasn't exactly in a position to insist I be prosecuted for doing so.
For a short while I considered upgrading that pepper spray to a gun, but that robbery sent that idea right out the window. I know that's a fear I don't care to deal with, and we now have a nice aluminum baseball bat near the bed--just in case. Colorado is a "make my day" state, so I'd be fully within my rights to shoot to kill an intruder in my home (and there've been efforts to expand that to our vehicles), but I already KNOW how to handle a bat, and that plus the adrenaline I'd be dealing with (Ambien or no Ambien) would be PLENTY to send the necessary message.
I freeze when I see a handgun, period. My IQ drops about 90 points that I really can't spare, I go into cold sweats, and I have about three minutes before I had better be in a bathroom.