The fucked up part about that goal is that the linesman couldn't give it another thought without being accused of using a camera to aid him, even if he wanted to check with Rosetti. I thought FIFA had banned instant replays from stadiums, but since everyone was pointing at the screen, that doesn't seem the case.
As for the usual "it doesn't slow down the game nyah nyah nyah", he was about 2 years off the last defender. Yes, in this case it would be instant. But I doubt one of those "foot or head" ahead cases would be so quick to decide. And since it was so blatantly obvious (at real time, I thought Tevez had just one defender between him and goal), it's a matter of refereeing quality, not technology.
Anyway, it was a shame. The game was being quite entertaining until the first goal. Then Mexico lost his head, conceded a soft second goal, and are more than likely out of contention.