Every time something like this comes up, I'm amazed by the number of people who say that they would react violently, and indicate that they are prepared to do so, either because they usually carry a gun and/or a knife, or because they're trained in specialized hand-to-hand combat techniques. Some of those people probably are trained/armed/etc., and a few are probably just internet tough guys. Who knows.

Me, I don't carry or own a gun. Never have, never will. I do carry a knife, but it's one of those tiny little Swiss Army knives. Not exactly an intimidating weapon. It comes in handy for opening envelopes or cutting a story out of the newspaper, though.

I'm a middle-aged man with creaky joints (one of which is artificial at this point, and another that will probably be replaced in a year or so). I take various medications, including one for a heart condition. I'm pretty realistic about my chances of coming out of a violent encounter unscathed.

It's a bicycle, folks. If I really thought a thief would take off at the sound of my voice, sure, I'll yell at him. Otherwise, I can always get another bicycle.