My question is, if the player had jumped, and fielded the ball in the air before it hit the crossbar (or crossed the plane of the goalposts), would it be live?
I tend to think not, since the Packers have several players capable of getting their hands more than 10 feet in the air (6'5" Jermichael Finley comes to mind), but did not send them to the end zone. On the other hand, Cobb was probably the quickest runner should the ball fall short, so I can understand why he was back there, even if it could have been swatted down.
I believe this practice was actually legal many years ago (pre Super Bowl era).
Leaping at the crossbar was declared illegal by the NFL (in 1969?), after it was in vogue for about a year. In 2003, the NFL also enforced a "running forward and leaping" ban for the protection of the airborne attackers and the kickers alike. The only legal block is hitting the ball coming off the foot, or jumping straight up.
Yes, the ball would be live. Much the same as blocking the field goal immediately after the kick, there is no "goaltending" per se like in basketball where you cannot block a shot that is on its way down. Blocking it by jumping and fielding the ball before it rings off the crossbar would be considered a blocked field goal and would be a live ball if that player were able to field the ball without stepping out of bounds. Crazy bounce and a hell of a kick, but if a big man were there, he may have been able to snag it before it hit the goalposts and received credit for a "blocked field goal".
That's 100% incorrect.
Quote: 2012 NFL Rulebook, p. 79
Goal-tending by a defensive player leaping up to deflect a kick as it passes above the crossbar of a goalpost is prohibited. The Referee could award three points for a palpably unfair act.
Since the kick was headed for the crossbar, and not clearly through, I think if GB had caught it, or knocked it down, they might have gotten away with it.