Everyone agrees that a series of failures and mistakes leading to the use of containment systems is totally unacceptable. Capping stacks and containment devices, while necessary and important, should never have to be used in the post-Macondo offshore world.
The same cannot be said for blowout preventers. BOPs will be used and will have to work when needed. No matter how carefully drilling programs are planned and executed, there will be hydrocarbon influxes into well bores. While most of these influxes will be “routine kicks,” the equipment must work and the personnel must be trained to use it properly and to function effectively as a team.
The DNV report on the Deepwater Horizon BOP failure included some unexpected findings. These findings will be discussed at the Joint Investigation hearings which begin on 4 April, and will hopefully be televised or streamed live. While attention will focus on specific components, BOPs must be evaluated as complete systems. What new risks have been identified? What are the options for addressing these risks? What risks are posed by the solutions? What other risks, related and unrelated, need to be addressed?
I doubt that there will be any argument with the DNV recommendations. These include studies on elastic buckling, shear blade surfaces, the effectiveness of ROV intervention, and well control procedures (including the sequencing of annular preventer and pipe ram closures); revised testing procedures for backup control systems; improved capabilities for monitoring of the status of BOP functions; and requirements for backup control system performance.
BOP stacks with redundant blind shear rams are becoming more common, and would generally seem to be appropriate for subsea wells. However, attention must be paid to the entire stack with the goal of optimizing overall performance and most effectively managing risks for the type of well that is being drilled and the site-specific conditions.
Bud's Offshore Energy (BOE) 
The shear ram is last resort and may be put the possible buckling into context ?, but prior to that all other BOP barriers failed : lower and upper annular and the 3 sets of VBR’s variable bore rams, which is not reassuring about anything on this BOP.
Further the possible losses of the communications electr. after the first explosion may have also damaged in similar ways the subsea hyd. accumulator supply via the rigid conduits on the riser, hence after several atempts to operate several functions on the BOP the useable volume and pressure available would have become under what is necessary to close this BOP versus the kick pressure. The rams having travelled forward does not indicate they are fully closed, and the control module does nor record that precisely, the surface computer do record volume/time/pressure , but off course all that is lost with the rig.