I realize it happens quite a lot but that doesn't make it less illegal.
I saw the first two or three punches in the sprawl position going to the back of the head. Those were game changing punches. Before that he was still trying to fight back, after that he was curling up trying to protect his face. Out of all the punches Silva threw in sprawl position not even one was 100% legal.
Here's a gif:
Now, this gif says all those ear strikes are legal (I'm only using it because it clearly shows you where Prater was hit). Well, as I see it they're not on the ear but well behind the ear thus making them illegal. Personally I don't know what the guy who made this was thinking. You can clearly see Silva hit Prater four to five times on the 'back of the head' area.
That's a reason for a DQ if I ever saw one.
Good post, but I have to disagree that it should have been ruled a DQ. If the ref thought the hits were illegal he should have halted the action, took a point away and see if the other fighter could continue and give him time to recoup.
In this case though, that one strike did not have an outcome on the fight in my opinion, but from the ref's point of view I can see how he thought there were several shots which hit the back of his head.
The only thing which surprises me is after watching the replay and even that gif you posted, how you can support not giving Silva a win bonus. But I think we're just going to have to agree to disagree.
EDIT: I checked the gif again, and I don't see the shots hitting the back of his head. I am trying to remain as unbiased as I can, and I think one or MAYBE two hammer fits hit the back of his head, but this is something that is going to happen when a fighter is turtled up and squirming around. I would agree with a DQ if I see a fighter purposely trying to hit someone in the back of the head, but if he is trying to punch someone on their temple and the other fighters shifts around during the exchange and accidentally hits the back of the head, it shouldn't be considered an illegal blow.
Following that same line of thought, the punch Matt Serra caught GSP with before GSP fell to the ground and got ground and pounded hit GSP in the back of the head. It was a fluke of course. But some people could say, "Technically, that shot hit GSP in the back of the head. Regardless of Serra intent, it is an illegal blow." GSP is one of my favorite fighters, I'm from canada, and if someone had said that, I would have called BS, and gave Matt the win he deserved.
And that's what I consider Silva's shot to the back of the head, a fluke. It wasn't intentional, and that one or two shots were not fight changing.