Peter G. Neumann maintains a long list of instances where people did not focus on failure adequately. The Illustrative Risks to the Public in the Use of Computer Systems and Related Technology is a curated archive of the Risk Digest. The Digest is a long tenured well known and highly respected mail list on risks of computer use.
Infoworld has a good list of 11 infamous software bugs. These are also good examples of failure to plan for failure.
The Financial Times has a good short article about the catastrophic effects of some spreadsheet errors.
Some people never ever learn.