jfruh writes: "In the world of high-frequency stock trading, every millisecond is money. That's why many firms are getting information and sending big orders not through modern fiber-optic networks, but using line-of-site microwave repeaters, a technology that's over 50 years old. Because electromagnetic radiation passes more quickly through air than glass, and takes a more direct route, the older technology is seeing something of a renaissance." Link to Original Source
Computers are unreliable, but humans are even more unreliable.
Any system which depends on human reliability is unreliable.