If your area is filled with good law-abiding citizens, you probably have lower crime rates.
A civilized society with low levels of poverty, good economic mobility, a good education system, a fair and effective judicial system and no drug war would mean there'd be less people committing violent acts in the first place.
When you're at the point where an armed citizen has to regularly thwart crime, you probably have major unresolved socioeconomic problems.
Not that I'm against a citizen's right to bear arms. Just saying that the goal should be to have less people motivated to commit crimes in the first place, not a bunch of would be criminals calculating whether or not they're going to encounter armed resistance.
Maybe its just the sad fact that bad news tends to travel more widely but I have yet to hear (on UK news) of a situation were an honest law abiding citizen has stopped a tragedy. I realize that their very intervention may have stopped a tragedy, making it not news worthy but I'm sure there should be more instances to justify that argument.
So if you happened to be walking down the street with a knife and you were not a chef on the way to work, you could be arrested.
My favorite independent site was taken out by the Righthaven copyright trolls, but you can start with this: http://www.nraila.org/gun-laws/armed-citizen.aspx ; each item is from the media.
http://blog.mlive.com/annarbornews/2008/06/customer_foils_ba...