Let me give you an example - last Friday we were having a cookout (at work, for lunch). We have one every few months.
An SUV pulls up. We don't know who it is. All we know is that it's 4 guys. One guy gets out, starts walking to the door.. bloodshot eyes, pants down below his knees, you know the getup - says he talked to "Kevin" and wants an application. There's no Kevin that works at our place, so one of our guys mentions "Keith" (who does work there) and the guy says "yeah, Keith". He gets an application, and goes out to his SUV.. for 20 minutes. He comes back in, saying he wants the "short" application. Turns out he wants to rent some equipment. We'd be happy to do it, but there was something really strange about this situation. We give him a credit application. He sits out in his SUV with the 3 other guys for 30 minutes. This is in the middle of the cookout, everyone's out at the shop, and I'm waiting in the office. It might not sound strange, but it was a tense situation.
I'm not going to get into race issues. I'm not racist. If this guy had been by himself, and not dressed in this manner, and not OBVIOUSLY under some influence of whatever drug, and not acting so suspicious.. I would've been happy to deal with him.
If this had been in any other situation, I would've been happy to talk with him. You just don't come in trying to rent heavy equipment stoned outta your gourd, pants below your knees.
Nothing ended up happening (except for them throwing several pieces of trash out of the SUV into our parking lot). I know one thing. I've never been happier I had a gun strapped to my waist. This may seem drastic - but I don't see it as drastic at all. The guy ended up not causing any trouble. He wasn't being a jerk or anything. That's probably 99% of the situations I'll encounter at work. I carry just for that 1%. I don't have it strapped to my waist constantly at work, but I do have it within arms-reach.
edit : PS, also, at our "parent" company where my dad works, there is a woman there whose ex-husband is nuts. He has tried running over people in the parking lot. He has come in threatening everyone. He tried to blow his brains out, but somehow missed. They have bulletproof glass there now (and this is in a small, nice town). My dad has mentioned that there are a few people carrying there. One guy has a shotgun in his office.
the way I see it - work is pretty much one of the more social experiences I have in my day to day life. People coming in, people leaving. You just don't know what's going to happen. It's called paranoia now, I guess, since nothing has happened; but if something does happen, it's no longer paranoia. It's being prepared.