The first instant replay was of the winning touchdown in a 1963 college football game between Army and Navy. But that's just about how people view the game -- more controversial and perhaps with more impact on games themselves is the use of replay by officials. Replay at its most extreme is seen in rugby, where a TV ref helps the on-field ref make decisions. Or remember the red card given to Zinedine Zidane for head-butting an opponent in the chest during the 2006 World Cup? The ref missed it completely -- until he saw it replayed on the big screen.
Sure, we can see a quarterback's arm in super-slow motion from almost every conceivable angle to discover (almost) definitively whether the arm had started its forward progress when the ball popped out. But should we? Certainly in this era of instant replay, fewer bad calls affect the outcomes of games. But the antiquated theory was that bad calls were part of the sport -- the way the ball bounces.