Ask HN: Best Lessons from Technical Postmortems?

From "Learning from Accidents" (Trevor Kletz):

Keep a 'black book' or 'memory book' in each control room, a folder of reports on accidents that have occurred. Do not include falls and bruises, but only accidents of technical interest, and include accidents from other plants.

Are there outstanding technical postmortems with good general lessons for software engineers?

Esp. interested in

- Incidents with software products (we all know Challenger) - Incidents written up officially and publicly - Fun reads