Blame?
I would first start with the post-approval environmental groups. BP was already given the green light to drill in shallower waters - manageable 500ft depths - and then they ride in and push BP out to depths of a mile to drill for the same source. This is a common problem for oil drilling: there is a lot of shallow coastal oil reserves that have been mapped to some detail but those who would access these resources get pushed out to more hostile, unmanageable territories. This extreme depth remains a problem in this catastrophe, as evidenced by BP's first endeavor to cap the well where it became blocked off as it was being lowered (crystallization build-up; ice, I am assuming?).
BP did bypass a
lot of safety concerns during construction.
http://www.usatoday.com/news/nation/2010-06-14-oil-spill-letter_N.htm
I don't have to say much more since the listed items, and others not mentioned but are easily evident, speak for themselves. On the other hand, I haven't read a specific report that explains whether the initial explosion broke open the pipe or the actual collapse of the rig broke it. If it was the former, all on BP in this department; the latter, and, after the initial disaster, it was out of BP's hands if the oil spill could have been averted.
The Administration is the last to blame. Their effort was tardy at first, insufficient when it came, and they keep tripping over foolishness and bureaucracy, seeking their only refuge in posturing. I would actually sum-up the Administration's efforts as "cowardly." Both BP and the Administration know that true management of the spill is out of their hands, and was out of their hands as soon as it was detected, but only BP was required to do something about it; by keeping their distance, the Administration looks frightened to accept any responsibility for the efforts to cap the well. They've left BP to play with to experimentation and, for their efforts, I do hope BP actually gets off better in history books than they deserve.