Last week I caught this story from the CBS Affiliate in Atlanta.
The report, which the news station even calls a "unintentionally hilarious investigation", takes a look at family dogs an their ability as "guard dogs".
The investigation included enlisting Jeff Schettler from the Georgia K9 Training Center. Schettler wears a dog bite protection suit, and then acts as an intruder going into people's homes while the owners are not present and films the reactions of the dogs. The story also interviews respective dog owners to see how they think their dog will behave.
Schettler enters into the homes of many different types of dogs: a couple of Border Collies, a Brittany Spaniel, a pit bull, a German Shepherd, a Rottwieler and a couple of Lab mixes.
The end result is that most of them are pretty lousy guardians. Most try to befriend the intruder. One dog even gets stolen by Schettler. The 'pit bull' tries to make friends while his lab mix companions bark at Schettler and even does tricks for Schettler to try to win favor. Only the German Shepherd really puts up any resistence, and that is mostly out of fear.
I think the report does a good job of noting that dogs without specific breeding/training to be guard dogs are not much good at it -- and also of noting that most people are best served by not trying to have guard dogs because they are not terribly good at determining friend or foe.
Overall, it's a pretty interesting (and at times funny) report and worth the time to watch.