It now appears likely that BP was deliberately cheating on blowout preventer testing:

… an oil industry whistleblower told Huffington Post that BP had been aware for years that tests of blowout prevention devices were being falsified in Alaska. The devices are
different from the ones involved in the Deepwater Horizon explosion but
are also intended to prevent dangerous blowouts at drilling operations.

Mike Mason, who worked on oil rigs in Alaska for 18 years, says that he observed cheating on blowout preventer tests at least 100 times, including on many wells owned by BP.

As he describes it, the test involves a chart that shows whether the device will hold a certain amount of pressure for five minutes on each valve. (The test involves increasing the pressure from 250 pounds per
square-inch (psi) to 5,000 psi.) "Sometimes, they would put their finger
on the chart and slide it ahead — so that it only recorded the pressure
for 30 seconds instead of 5 minutes," he tells HuffPost …

Many people already chasing after an industrial witch will shift focus on to BP, as opposed to the previous witch du jour, Halliburton. Given the potential, likewise, that a hydraulic
line leak in the blowout preventer may be the root cause, this is
valuable. However, I think this is the key information today, that will
probably go less observed:

… [The whistleblower] Mason claims that a BP representative was usually present while subcontractors performed the tests …

The question is: "Why wasn’t a representative of the US Minerals Management Service present to verify the validity of testing?"

In other words, it is shortsighted to simply start and stop with BP on the blame for test result falsification on critical safety equipment such as blowout preventers. The real fault lies with the Federal
government – it is news to noone that industry will lie about virtually
anything to cut costs and put more money into corporate pockets. It’s
the role of the Federal government to insure that industry doesn’t get
away with this when companies like BP inevitably try to falsify tests,
and the hearings in the Senate should involve questioning the current
and past heads and officials in MMS in order to determine how it is that
tests could be falsified ever let alone in number. The witch to burned
is the witch of corrupt public officials.

The Deepwater Horizon disaster was utterly predictable. Preventable? Perhaps not – that is the lesson of attempting to exploit resources at or beyond the ability of an industry to guarantee safety and
reliability. But the predictable this disaster was, and beyond the fact
that MMS didn’t demand sufficient disaster response plans from BP as a
condition to authorizing drilling, it now seems quite plausible that MMS
looked the other way while BP officials falsified test results on
blowout preventers much like the one sitting under a mile of Gulf water
spewing oil.

The Federal government should force BP to pay for the recovery and analysis of the totaled blowout preventer once the leaking well is stopped from flowing by intervention wells. The Deepwater Horizon
itself, a massive structure in the tens of millions of kilograms, can
never be raised and without a doubt will rust on the bottom of the Gulf
with hundreds of thousands of gallons of toxic diesel fuel on board for a
very long time. But the preventer may be recoverable and if it is it
could provide valuable forensic evidence.

Still, the first thing the Senate hearings underway should do is grill the MMS officials who signed off on BP’s drilling plans. The first questions these officials are asked should demand a detailed
explanation of what sort of tested were done on the Horizon blowout
preventer, who certified these tests were real and valid, and what due
diligence MMS did to insure that an organization like BP, with its
famous wanton disregard for environmental health and safety issues, did
not get away with falsifying any test results.

If these questions are not asked now, there is no hope whatsoever for sound Federal enforcement of regulations on extraction. While BP and the industrial players must be held accountable for every last cent, and
while they should not have any sort of profit being made during the
extent of this spill, the real goal must be to drive a stake through the
heart of corruption in government enforcers of industrial regulations.
Corporate businesses will always try to break laws and rules to
put money in their pockets. The government must be the bulwark against
this behavior. The entire Bush-era MMS leadership should be brought in
front of the Senate as soon as possible and the hearings not concluded
until all of the failure and corruption is revealed.