Guys, I am always interested to read this kind of thread. I agree with most of what has been said, but honestly, many of you are under an incorrect assumption. Or outdated training.
You need to train realistically. And if you do so, you will fast realize that you are not going to stand there and draw and shoot when someone is coming at you. The 21 ft rule is total BS if you know what you are doing and have trained.
It's very simple. Whether the bg comes for a gun fight, a knife fight, or a baseball bat fight, you must move. If you stand still, the best you will get is a draw, which means you both bleed. Move first, and keep moving. Practice drawing on the move. Practice shooting on the move. If he's charging you, the distance isn't going to be that far. You'd be surprised what you can do with a little practice. How do you practice? Get an airsoft replica of your carry gun. Gear up with it, and have someone come at you with protective gear on.
It is best to do this for the first time under competent instruction. I recommend Gabe Suarez. I just attended one of his courses a month ago, with another one last year. Geared up with the airsoft, a fast, skinny guy charged me with a training knife. I beat him at 12 ft. And guys, I'm slow. I had about 6 hits on him, in the face and chest, before he caught me, and I admit I slowed down, because I could see the hits, and I felt sorry for him. Yes, they sting. He had a mask on, but the body shots will leave welts (my turn was next). The draw was from concealed, IWB appendix carry under a shirt.
For the rest, I carry every day, anytime I am out of the house, except for at work, because I need my job. Other than that, I go where I want to go, and I am carrying. If they don't like it, the worst they can do is ask me to leave. And I have never been called on it, because I know how to conceal the weapon. If anyone asks you about it (other than an LEO) simply mutter to them about it being a cell phone, Ipod, or one of the other things people carry on their persons. Then ignore them and leave.
At home, my glock goes on a stand at the foot of my bed, until I go to bed when it moves to the nightstand. I live alone, in a small place, and I can get to that nightstand very quickly from anywhere.