Well, the three to five second delay it takes for the video to be transported from London to New York. The Times has a very cool article about how 325 hours of daily video is recorded each day, and sent across the pond, where NBC proceeds to hold onto it until primetime.

“What we place on the shoulders of Dave each Olympics is enormous growth,” said Gary Zenkel, the president of NBC Olympics. One year, he said, there was the transition to high-definition; another year, the addition of selected online streams. This year, for the first time, every single event will be live-streamed on NBCOlympics.com, and a handful will be shown in 3D on a special cable channel.

The volume of video — roughly 325 hours’ worth a day — must be carried to the United States on a complex series of circuits that are diagramed on a wall in NBC’s work space. “We call this the subway map,” Mazza said proudly. . . .

Sending so much video to the United States, a step also taken for the Beijing Games, also allows for more work to be done there, saving money for NBC. Five control rooms in New York are dedicated to the Games’ coverage, as are dozens of editors and producers. It is almost as if the engineers have erased the Atlantic Ocean off the map — but there is still a 3.5-second delay for the video to and fro.