@Bennet,
All good points, Bennet, but some will consider an openly carried gun to be a challenge. Anyhow, it isn't bad to leave the possibility that an apparantly unarmed person might indeed be armed.
As you noted, an openly carried firearm could definately become a challenge to the crooks, and it is hard to have a conceled weapon meet the standards of accessibility, effectiveness, and remain truely conceled till needed.