Oakleaf's point about conservative football was spot on. We've all tired of watching the McCarthy/Capers conservative game.
I can only guess how difficult it was for McCarthy to go for it on 4th down. It sent a message that the Packers were out there to win it, and nothing would stop them. The fact that they didn't make it was more because of the play itself, but what was established on those 3rd and 4th down runs was that the Packers were not afraid to run into the teeth of the Giants defense, so be prepared.
My first reaction was; "Why?" Then I realized the message he'd sent, and in all honesty, my wife and I looked at each other and both said; "It's all over but the shouting. We're going to win this one!"
Not only was a signal sent to the Giants, but one to our offense. He trusted them to make that play. He also sent a message to the defense. He said he trusted them to stop the Giants, on a short field.
Now, you can believe none of that came out of that series of plays, but in fact, it did. There is nothing stronger than the psychological part of the game of football.
If you played it, and your team was a winner, you know the psychological edge you can get over the opposition. As soon as you drop that hammer, it's all over for them. Ask the Giants.