All of this talk about surprise and advantage may well be true, but there is something else to consider. Granted, most criminal element isn't very smart, but every now and then one comes along with half a brain. In that situation, they will look to try and maximize their chance of getting away with a crime. Let's say someone is going to rob a bank or a store. If they are smart, the first thing they will do is identify anyone that might cause them a problem and eliminate that problem first...without warning or notice. So, if you are in a store with an open carry weapon, you just made yourself a target that you will have little or no time for self defense reaction. In many robbery type of situations you might not even need to present your weapon. If there is not a direct threat to you or anyone else, it would be a bad idea to escalate the situation. But if the criminal can see you are armed, you might not have a choice...and that could end badly for you or others. Basically, creating a deadly situation that otherwise would have never occurred. If I am in a situation that I would need to defend myself, I would want as much advantage as possible and telegraphing that I am armed takes that advantage away.