
Its not 'dominance' ie not 'im more important than you i rule this house', (and i would say that as i dont believe that dogs think that way at all).
What it IS likely to be, is dogs needing to spread their scent around to feel like they belong, in young dogs its not particularly rare, some of my dogs have done it here, my friends bitch went through a horrendous phase of running into my room and peeing either on my bed or on dirty clothes on the floor, she grew out of this though, as did my own dogs.
Notably the cases in this thread mention dogs doing it when allowed into places not normally open to them, nad diong it when left alone and presumably anxious, backing up my idea that its to do with feeling like they belong and NOT to do with wanting to become dominant over anyone.
Very badly anxious and stressed dogs will sometimes do this in their OWN beds.
Em