http://espn.go.com/blog/nfcnorth/post/_/id/8759/nfl-offers-context-of-face-mask-ruling
The Rule Book describes the penalty as follows:
"Penalty: For twisting, turning or pulling the mask: loss of 15 yards. A personal foul. The player may be disqualified if the action is judged by the official(s) to be of a flagrant nature."
The Rule Book describes an approved ruling as it relates to facemask penalties (page 81).
"A.R. 12.12 - Third-and-10 on A30. Runner A1 runs to the A33, where he is tackled by B1, who incidentally grasps A1's facemask on the tackle, but it is not a twist, turn or pull. Ruling: A's ball, fourth-and-seven, on A33. No foul."
This article states that it should not have been a penalty. I disagree. From what I've seen of replay and still photos, Rodgers does turn his head. At full speed, viewed from behind, it certainly had to look like a penalty to the ref who threw the flag. Could it have been overturned on review? Possibly, but the ruling on the field was a flag so if they could review this and the umpire sees contact to the face mask AND the QB turning his neck or head, then he would have to uphold the call.
I supported the 2008 rule change that took 5 vs 15 yard judgement call out of the refs hands and i still do. This is either a penalty or a great acting job by Rodgers. Give the man an Oscar!