I could see a criminal taking out a person who is open carrying because he or she is an obvious threat.
Imagine standing in line at a store that is about to be robbed. The robber comes from behind; he notices you have a gun, so he puts two in your back.
Concealing obviously makes you less of a target in robbery situations. I'm sure in some situations it prevents crime because not all criminals are killers, but I'm not one to take that kind of chance. I usually assume the worst.
It's a big leap from armed robbery to murder. It's not like there's a shortage of 7-11s and gas stations. When you hear about armed robbery, very rarely are shots fired. That said, situational awareness goes a long way, regardless of whether or not you're carrying.