That is what all this complaining is about? From what I've heard here, I though he didn't extend his arms at all.
His arms are fully extended. Any more effort to catch the ball and he doesn't stay inbounds. If he was where he needed to be to catch the ball he probably would have been out of bounds due to his forward momentum.
Throwing to the back of the endzone to a running receiver is a bad throw. The receiver can't speed up to catch the ball nor can he slow down enough to stay inbounds.
Ginn was open at the 15 (along with some uncalled illegal contact by the CB) and the CB is toast from the beginning (slowly walking backwards against a sprinting receiver), but the ball doesn't show up until 25 yards later in the back of the endzone. Pennington waited far to long to throw it and his weak arm just made the timing worse. If the pass gets to Ginn closer to the goal line its a touchdown.