i agree with your theory of pain being inflicted due to one of the three main reasons. In my own personal experiences with my Master pain is normally caused by the first two. We don't participate in humiliation play much if any at all. There are occasions, however, when pain is inflicted by accident during playful activities such as a stray bite in public or a slap on the leg as a reprimand from previous misbehavior. During Master's last visit to see me this became a more prominent problem, but we are working through that. i just had to remind Him that even though i can take a beating in bed (i.e., back side region, and the like) i'm still fragile.