It has been reported elsewhere that oil is seeping through cracks in the Gulf of Mexico seafloor near the Deepwater Horizon site.
It has also been reported that the well casing (the concrete tube that extends vertically beneath the seabed) was breached during the Deepwater accident, and that oil is leaking through the breach.
The seafloor in this area is about 1,500 meters beneath sea level, and the temperature of the water near the seafloor has been reported to be about 5 degrees C. According to phase diagram from the DOE, such conditions would make it possible for stable deposits of methane hydrates to exist for the first few hundred feet beneath the seabed.
Given that the area is rich in natural gas deposits, it is a good bet that the sediment for the first few hundred feet below the seabed (which supports the top of the casing) is a matrix made up of rock, mud and methane hydrate.
The oil in a reservoir such as that tapped by the Deepwater Horizon can be as hot as 900 deg F. If hot oil is escaping from the casing or from the breach in the caprock that is below the casing, this could easily cause the hydrates to melt, meaning that voids would develop in the sediment around the casing. In other words, the sediment around the casing may be in the process of becoming porous and unstable. This would explain formation of cracks in the seabed and the seepage that was recorded by the ROV's cameras. If this goes on long enough, the sea floor around the casing could collapse. The casing could lose its lateral support and fracture, which would allow unrestrained flow of oil from the underlying reservoir. Accordingly, a solid matrix of cold hydrates and dirt may slowly be in the process of being replaced with a fluid, upwardly migrating slurry of warm oil and dirt, and it is apparently close enough to the surface already that we are seeing cracks in the sea floor and oil seeps.
I hope I'm wrong, because this could end badly.