Actually, as I understand it the emergency blow-out preventers were tested routinely ten days before the explosion and passed muster. From the looks of the explosion (see my link to images) a HUGE amount of force was unleashed. I am not sure anyone knows how the explosion occurred. In any case the whole prevention system was crushed or torqued past operation, it appears.

If they're lucky they'll be able to drop some huge steel boxes on top of the well head and pump the oil out of them.

A