In late 2007, UK government workers lost two computer discs containing personal and banking data for approximately 25 million residents, information with an estimated black-market value of $2.5 billion. In early 2008, a failure at an outsourced data center in Denmark disrupted the operations of its clients—knocking out a major bank’s ATM network and halting milk delivery across the country. Then, last September, a network failure stopped trading on the London Stock Exchange on what would have been one of the busiest days of the year.
A version of this article appeared in the May 2009 issue of Harvard Business Review.