You could write a book on all the times spreadsheets have done something dumb. You could even follow up with a sequel covering times humans did something dumb and their spreadsheet did nothing to stop them.
Below are some of the terrible, horrible, no good, very bad times when spreadsheets ruined everything.
Kicking off our list is a 2010 study by Harvard University economists Carmen Reinhart and Kenneth Rogoff. "Growth in a Time of Debt" argued economic growth was negative 0.1% in countries with high levels of debt.
This paper drew considerable attention from policymakers. Undoubtedly, being published in the wake of the Global Financial Crisis (GFC), when debt was approaching historic highs in many countries, helped.
How did MI5 (British secret service) manage to make a thousand phone bugging errors, with shoddy spreadsheets of course.
A spreadsheet formatting kerfuffle caused Her Majesty's Secret Service to apply for data on the identity of telephone numbers ending in 000, rather than the actual last three digits. The only way this story could have been better is if the error had landed on 007. Sadly, we can only dream.
Phone numbers are now checked manually. Good move.
Time for a 2-for-1-deal!
For some reason Westpac and Barclays are unaware you can delete cells. If you like, you can even delete cell contents, leaving your favourite cells safe and unharmed.
Westpac's solution was much better, simply make the cell background the same colour as your contents. Genius!
A frantic Westpac was compelled to halt trading on its shares and deliver its annual profit briefing a day early when research analysts successfully removed the black background.
Even worse than colouring in cells is 'hiding' them, as Cleary Gottlieb (representing Barclays) discovered during the GFC.
Turns out when you convert a spreadsheet into a PDF, things like hidden columns can become unhidden. Which can be a pain when the hidden column is a list of things not to buy and your PDF is a buy order.
When in doubt, make a backup and delete those cells.
The above examples epitomise some of the problems with Excel databases (all spreadsheets, really). Stop using spreadsheets for little things like global financial policy, surveillance of suspected terrorists, and purchase agreements worth millions.