Very true. But I was thinking of their deterrent value, not their defensive/offense capabilities. It's their bark, not their bite, that makes them valuable.

I'm far more dangerous than my dog is, but his hearing is a lot better than mine, and he's a light sleeper. He stays inside at night, and barks whenever anyone approaches the house. A burglar won't have the advantage of surprise over me. My dog's considerable protective instincts are just a back-up.