If they do, it could be because they want to feel more like part of the family, or it's just a particular animal's personality and that animal was matched with the person meant for it.
@AJs:
See, Dan? First you tick everybody off, now you make everybody cry.
But you're still not getting off the hook that easy. You will NOT be banned and in fact will be required to stay. :D
What?! That's it I'm going back to my stupid jokes!
That is a happy ending! My SIL's boxer ran out the door one Christmas morning at the other SIL's house. We all watched in horror as she dashed into the street and ran INTO an car. She bounced off the passenger door, and seemed completely unphased!