According to MMAJunkie:
Matt Hamill suffered a dislocated left shoulder during his disqualification win over Jon Jones at The Ultimate Finale 10, which took place this past Saturday, Dec. 5, in Las Vegas.
It appears the injury occured on the huge throw that Jones used to take Hamill down to the mat. If you recall, as soon as it went to the ground Jones was able to take full mount without any resistance from Hamill. Hamill was able to defend himself, probably out of just survival instincts, but he wasn't able to try to buck Jones off or give up his back or anything. I don't think it would have mattered had the shoulder not gotten injured, but it does give some explanation as to why Hamill did so little to try and get Jones off of him.