What a bunch of pathetic pussies on this board.
1) If more people are carrying, then yes, I do believe the chances of this kid walking into the movies and blowing people away are reduced. Obviously, he didn't turn the gun on himself afterwards. He still wanted to live. He didn't go into the theatre with the intent of being harmed or dying.
2) True, I don't think most people would be able to effectively combat the shooter if they were carrying. However, I do feel they could effectively reduce the total loss of life. If I start popping off shots from the side and he sees me, his firepower gets aimed in my direction. Sure, I may go down, but I buy everyone a little more time to escape/evade to safety.
What are the risks? Your hero with a CC permit does take out a crowd member. It could happen, but to this date, there has yet to be a reported shooting incident where an innocent bystandard was killed by a CC holder using his weapon.