The dude with the shield kept holding his arm out over the shield. I kept expecting the longsword dude to take his arm. How do the rules treat arm and hand hits? It looked like a nice juicy target to me. 
Hand targeting is illegal in the SCA due to the force of the blows, and targeting the arm is considered a bit 'cheesy in the West Kingdom but there is no restriction on taking the arm. The legal target area is from 1" above the knee to 1" above the wrist and everything in between.
The reason I think that Marc did not take Rorik's arm is that it would have been hard to land a sufficient blow without having Rorik nail him in the head just before he did it. You can see a few glancing arm shots in the video itself showing hw hard it was in those contidions to land a good shot period (mud, snow, rain, wind, cold).
Personally I feel that, as we are all supposed to be armoured equivalent to that which was worn at the Battle of Hastings in 1066, Rorik's stance is "Gaming The System" as no man in his right mind would put out his hand in such a way that would risk losing fingers from a flicky shot so He is effectively using the Rules to close the line of attack instead of good position and shield work. What he does may work in the SCA, but it is still bad form, especially in the SCA (and that stance is hard on your shoulder too).
For curiosity's sake: What shot are you seeing?
