Not trying to get into the "criminal mind" here but crime is a business and the "risk" has to be worth the "reward."
Crazies, dope fiends and wacko's aside. A daylight armed robbery on a gun store with an inventory, camera's, alarm system with two or three employee's is something for the movies or t.v. A robbery on a Ma and Pa shop is a possibility. A very good possibility for that matter and something we read about quite often.
99.9% percent of your "scumbags" or "preditor's" will break in at night or take the path of least resistance i.e. closing up and when you are in a hurry to get out, locking the front door, hiding in the bathroom standing on a toilet in a stall, walking to the car and then being targeted, or something with the least visibility to them and greatest vulnerability to you being the potential victim.
Again, nut jobs aside, and not saying it won't happen and has not happened but the probability is low.
With that aside, armed at work. You, bet I would be. Normally I have one on the hip, one in the pocket and a knife, if all else fails. Oh yea forgot, the "politically correct" cell phone to call 911 after the fact.
And what would be recommended, something for personal protection such as a firearm (first choice and know how to use it and its limits) and second a way to notify authorities as 99.999999999999999999999999999999999999% of the time you are on your own until they respond.
Someone said it better than I could ever, "an armed society is a polite society"