LOL, like many others have already said, my Yorkie barks when I don't pay attention to her, but it is a bossy bark aimed at me, no one else. So its not random
She barks sometimes when playing with Nappy, or if strange sounds but she is not a yapper by any means. My Maltese, on the other hand, barks the second she steps out the door to announce her prescence to the world.