Actually, on a more serious note, most of the people I've spoken to who have been burglarized were hit by people they knew. I am fortunate to have never known anyone like that, but whenever I ask that is usually the case and it amazes me.
About eight years ago my mother left her home in the care of a friend she'd known for several years. That so-called friend loaded a UHaul with my mother's stuff...a lot of antiques and irreplaceable family heirlooms. When my mother came home...well... you can imagine.
There are a lot of strangers who will not bother a house with dogs. In fact, they will go for a house with a security system before they bother the dogs. But, if it is someone the dogs are familiar with, then they may let them right in. And the culprit could be anyone...the big brother of our child's best friend, for example.