I for one think dogs work well as alarms, but not so much as guards. Both of my dogs are great at letting me know when something is out of whack (snake, person in the yard, car comming up the driveway at night, est.) but not barking at stupid crap. That’s about as good as you can get. If they bark at stupid crap, you stop paying attention to them and some others don’t bark when they should. One is a malamute (he can be intimidating) the other is mostly blue healer but still a pup.
On a funny note:
A tarp blew into my yard the other day and freaked the dogs out (it was late at night). The healer was running to the side yard, barking, running to the door, barking at us and kept going back and forth. I grabbed my 12 GA and went out into the yard figuring it was a snake or something. I don’t know what it is with dogs and tarps, but I was really impressed with how she let us know. She’s too smart for her own good.
