The way I remember it, and I really want to go back and watch a replay of it, was that Jennings caught it and took two steps before being stripped on the third and fumbling. In which case it is a catch and a touchdown. It would have been a fumble if it had been anywhere outside the end zone in the field of play (by the way, for those of you asking if it was a fumble, I hope you're making a joke).
The thing everyone is getting caught up on is that everyone is saying two feet down equals a touchdown. No it doesn't. You don't have to get two feet down, you have to make a football move, which taking two STEPS is (I believe I've even seen one step considered a football move). If anyone is watching the Arizona-San Fran game right now, you'll recall that the second Arizona fumble was a catch and fumble because he was stripped as he took his second strip by Willis (beautiful play btw).
The issue with going to ground is if you catch it and you are being tackled as you catch it as was the case with that Oakland receiver. That situation is nothing like Jennings as we've pointed out that Jennings was actually still running. For the argument that the defender touched Jennings shortly after catching it and therefore meaning he was going down I ask this: if a receiver catches a pass and as soon as he does a defender jumps on his back, he then runs with the ball for 20 steps and falls to the ground, losing the ball when he lands, is that incomplete? Clearly that would not be the case because he was not going down in spite of the contact and he made a football move after the catch.
That said, if Jennings bobbled it the entire time leading up to the strip (which I don't believe he did, but again I want to see the replay) then it would be incomplete. If not, it should have been ruled a touchdown.
Born and bred a cheesehead