Tweak, as VB says, it depends on the state. Plaid is in Florida. They recently added a change to their laws that allows a homeowner to defend themselves or their property if there appears to be a danger. No requirement on how close, if the other person must have a weapon, etc. Reasonableness still applies, but the threshold has been severely reduced. I think it is called the homestead law or something like that.
As far as your CCW law and shooting someone on the street if they are mugging you, it would seem that that might be true, only if the other person did not have a gun and you had options, such as running/backing away, giving up your wallet, etc. Otherwise, I would imagine the threat of the use of a gun in a robbery or mugging would allow any citizen, even without a CCW, to use like force if options were limited and the threat is real.
California is a lot like the last scenario, but even more picky about your posture. For example, if someone breaks down your door and it seems like they are there to rob you, you can't shoot them. You must first see a gun, determine that there is a threat of it being used (pointed at you) and have no other options or exit. Basically, what they want you to do is cower in the corner of your bedroom with the attacker's gun 2 feet from your head before you can shoot. Juries don't usually buy it, though, so those that have shot their attackers from even 15-20 feet away usually get a slap on the wrist. Again, what is reasonable, based upon the threat and fear.
I persoanlly feel the sound of racking a semi-auto or a shot gun should deter most robbers. I have personally witnessed this while out travelling in my motorcoach. Guy three spots down had someone banging on his door in the middle of the night saying his rig was on fire and to get out. According to the MH owner, he peeked out and caught a glimpse of the guy who had his buddy waiting just around the corner of the door with a knife. Three spots away I heard the shotgun load. He tells me the guys muttered, "The guys got a gun, what do you want to do?" to his partner, and then they left. Someone got the plate and they were arrested 20 miles down the road, trying the same thing at a truck stop.
