from my experience now that my ddb has matured some ive noticed her to be protective in subtle ways with new company. she will stand by them and lay in their lap as if asking for attention.. but it is really her watching them closely, as i had a friend joking around one day and he punched me in the shoulder and he almost was bitten in the butt. i warned him not to joke around like that if my dog is around heh :P and my ex girlfriend got very angry one time and attacked me and my ddb jane took her down to the ground by her arm but did not hurt her. so in my opinion a ddb is a unseen protector until the time it becomes needed to protect. the more you bond with your dog the more likely it is for it to defend you. there is also training schools for personal protection dogs if you want to have a well trained protector :)