There were some people who drilled very straight tunnels and laid fibreoptic cables through them. They knew people were willing to pay a lot for this, but didn't realize it was High-Frequency-Traders wanting a faster connection between Chicago and NYSE.
Some producers of intermediate goods see demand fluctuate from month to month, but have little idea why, or whether the fluctuations will persist.
Nice article about paperclip industry, I'm sure it will be of considerable interest to many LessWrong readers.