Also, it may not be an everyday occurrence, Scott, but there have been random dogs that have helped people out before. I remember a story from a while back where a stray attacked a thief that was trying to beat and burglarize some woman late at night. I guess she was screaming, and he went running at the guy. My dog did that too, even with people that weren't members of the family. Sometimes if you were just playing around with a friend or goofing off, and that person was like laughing or screaming and you were "assaulting" them in some manner (like when I was wrestling around with my cousins, or... uh... doing questionable things to a girlfriend of the time), she'd run over and start looking concerned. If you didn't stop, she'd start pawing at you, and if anyone's reactions got particularly tense, she'd occasionally even jump at you and try to push you out of the way. It was me, so she wouldn't bite me, but it was plainly obvious that she was bothered. It wasn't just that she wanted to play or anything, there was a decided difference. Some dogs just seem bothered by a person who appears accosted in some way.
Dolphins and people share a strange relationship, though. There aren't years of domestication and such to explain any of it, yet you have these instances that lead to cool stories of the prior kind. Makes you wonder.
