This is part of why I have dogs. As a kid we lived in a bad neighborhood and so we had 3 big dogs. Neighbors got robbed more times than I probably am aware of (I KNOW at least 3 times in 5 years) but we never got bothered. In my adult life, I've owned two houses and always had at least 2 dogs; at both of my homes, my next-door neighbor has been robbed despite both houses being in decent middle-class neighborhoods.
Anybody who opens my garage door now is going to find three dogs waiting! I don't know if they'd actually bite anybody, but most robbers, upon hearing multiple dogs barking, aren't going to try to figure it out. They'll move on to the quiet house next door!
Plus I just like dogs. They're some of my favorite "people". ;-)