Yeah, the whole "criminals will just counter with bigger guns" bit is horseradish. Criminals are just quite predictable -- they want to get their money with the lowest level of effort. If two houses have dogs and good locks, and a third does not, they're going to hit the third house. They're not going to spend time and money on dog tranquilizers and sophisticated lockpicks.

Likewise, a gun is a gun. Even a .22 is plenty enough to maim or kill a human being (remember, aim for the head). If a criminal knows darn well that the members of a neighborhood watch may be armed, he will avoid the area. These aren't super-creatures who mutate and evolve to counter every effort. They're just people. Usually lazy people.

An armed neighborhood watch is a fine idea for an area in which the police cannot or will not keep the peace. The only issue is making sure that the people on the watch don't let it go to their heads. One innocent shot down will be all the excuse the city needs to break them up, so carefully, lads, carefully now.