The most disturbing element of deep water oil extraction is always going to be the unknowns that are ignored in favor of ambitions for getting and selling oil. The biggest unknowns include the pressures and physical challenges of installing, maintaining and operating equipment in places that have never been accessed and which cannot be accessed by humans.
It is all just educated guesswork combined with human decision making and judgment that has been demonstrably unacceptable, given the risks of greater disaster than the BP oil spill has caused. If a company that had all but one of over 700 egregious safety violations can continue to operate in even more controversial deep water extractions, than it will be no wonder if another major disaster happens.
The first and worst unknowns are the sizes of the oil caches, some of which could go on for hundreds or thousands of square miles at for unknown depths. Given the fractious, porousness and fragile nature of the balances that are maintained in the Earths uppermost layers of crust, it is a true risk that, by removing vast amounts of gas and oil that has maintained a steady state and pressure, the operations will trigger adjustments that could result in cataclysmic earthquakes, tsunamis and massive toxic releases of gas and oil.
The dangers of methane and the risks of a massive methane release is on the minds of many as the status of the ocean floor in the Gulf of Mexico is being questioned. It is being questioned whether there is a huge and immeasurable bubble of methane beneath the surface of the ocean floor in that region, and questions are being asked about the world killing event that could occur if a massive methane release were to occur as a result of interfering with the balance of things in the region. Simply put, methane kills air breathing life as soon as it reaches enough concentration in the air to deplete oxygen. If enough methane is released to form a concentrate in the whole atmosphere of the planet, then oxygen dependent life is in jeopardy, no matter where it exists.
There are the physical threats of a massive oil and or methane release. This could create tsunamis and disruptions of the crust, especially where tectonic plates are already in states of tension that might be released. If adjustment of the tectonic plates get involved, the word "Tsunami" is not enough to describe the potential of a 300 foot tidal wave.
Finally, the long term atmospheric changes and poisoning events that come from overwhelming introductions of gases and toxins into the air, land and water are enough to make mass extinction a long and horrible process. As humans and animals are poisoned, it might take a lifetime or a generation for the digestive, metabolic, neurological, reproduction, and other problems to show up. Exposure to the oil and gas will be sickening and killing people, while damaging offspring for generations to come.
As food sources die out, famine and loss of ability to make a living will be a permanent problem in the lives of millions of people.
There is the inability of aquatic and land plants to contribute oxygen to the atmosphere and habitat for food animals. There is the disrupted chain of living things that support, control and relate to each other in ways that are not understood.
Finally, no one knows how much true and complete damage the BP oil spill has done because the event is not over and the true damage is not yet known. But the biggest natural disaster in US history is something that should not fade from the news cycles, because there may be much more to come.