In 2006, Alitalia Airlines, the official airline of Italy, made a slight mistake on its website regarding international airfare from Toronto, Canada, to the island of Cyprus. They advertised business-class seats for $39. It was supposed to be $3900, but somebody left two zeros. Two thousand tickets were immediately snapped up and it cost the airline $7.7 million. Somebody messed up.

In 1990, 75 million phone calls across the United States went unanswered after a single switch at one of AT&T’s Switching Centers suffered a minor mechanical problem and shut down. Like a domino, it sent a message to other centers around the country, which also caused them to shut down. The cause was a simple data entry, of one error, in a single line of code. American Airlines alone estimated they lost 200,00…