The New York Times posted a very moving article on the final moments of Deepwater Horizon.  It does a good job at describing the events from the viewpoint of the survivors, and highlights a couple of very important issues that might have mitigated some, or all of the losses:

• Exhaustively planning for potential scenarios.  Employees were trained all right, but they were not trained to handle a blowout of that magnitude.  Perhaps a proper systematic HAZOP could have helped identify such scenarios.
• The need for proper employee training.  The article describes some inexperienced employees who didn’t even know an emergency plan existed.  All too often these plans collect dust in the control room never to see the light of day.
• The importance taking emergency evacuation simulations seriously.  The article stated that emergency evacuations were practiced, yet the survivors failed to follow them when an actual event occurred.