http://motherjones.com/blue-marble/2010/06/bp-mms-ignored-warning-s...

New documents released over the weekend to the New York Times show that both BP and federal regulators at the Interior Department's Minerals Management Service had plenty of warning that the drilling
operation at the Macondo well site was plauged with problems—dating as
far back as June 2009. But despite known issues with the well and the
blowout preventers, the operation continued until the April 20 blast.

One document reveals that on June 22, 2009, BP engineers noted concerns that the metal casing the company wanted to use on the well could collapse under high
pressure. BP used the casing anyway, after overriding its own design
and safety standards. Other documents released this week
reveal that the company knew that there was "unlikely to be a
successful cement job" on the site and that the casing would be "unable
to fulfill M.M.S. regulations."

BP also knew that there were problems with the blowout preventer, or BOP, which was supposed to shut off the well in the event of an emergency. The BOP clearly failed to function following the explosion
of the well, which has now spewed oil into the Gulf for 43 days. As the
documents note, the BOP was found to be leaking fluids on at least
three occasions prior to the blast, which would impair its ability to
function. But because of the other known problems with the well
casing—drilling mud falling into the well, sudden gas releases, and
loss of "well control"—the company asked federal regulators at the
Minerals Management Service to delay a mandatory test of the BOP.

The MMS first rejected their request for a delay, but then relented. Here's the email issued to BP granting the request:

It's becoming more and more evident that BP knew about numerous problems with this drilling operation, but chose to proceed anyway. But it's also apparent that MMS also knew about these risks and allowed to the company to operate. The Times piece also highlights the fact that federal regulators gave little scrutiny to an April 15 request from BP to revise its plan to deal with a blockage in the well, approving it in under 10 minutes. That was just days before the blast—but it doesn't appear that MMS attempted to question what was going wrong with the well.