I work with an animal rescue. Most dogs are bred to be loving. That's what they do. I would hope though, that the barking would deter most but the very hardened criminals. I can't imagine a burgler still entering a home after the dogs have 'sounded the alert'. They could be walking into an owner who's now had time to get the shotgun ready.

I also expect their barking to alert me. Although I do know they would protect me but probably not the house.

In 2005 I was in the shower alone in my house when it was broken in to. My three Yorkshire Terriers alerted me with their non-stop barking that something was very wrong. When the Yorkies followed the intruder upstairs to the master bedroom, they positioned themselves outside of the bathroom door to protect me. Since I relied upon their barking to indicate that something was wrong, I stayed in the shower and waited for them to stop barking to let me know it was safe to come out of the bathroom. I will never know whether or not the intruder was armed, but I do know that those dogs saved me from harm and possibly saved my life that day.