There are some instances where the dog of the family is protective to a particular member of a family and can bear it's teeth or snarl if someone gets too close to the person. If the family are aware of this then they should warn whoever comes to call obviously. But if it goes wrong and a visitor is bitten will the dog have to be put down if this happens, I mean the kind of bite that breaks the skin and draws blood? If the visitor wants to take it further is there anything to stop the dog from being destroyed?