I'm a little confounded that, as British Petroleum and the US Gov't (pretty much in that order) generate options and possible solutions to the oil leak out in the Gulf, I've not heard anyone mention demolitions.
I know more than a little about demolitions, more than I ever wanted to know about fluid dynamics, and absolutely nothing about oil drilling, petro-engineering, or marine geology. Still, if we think we can hit a "bulls-eye" at 5km subsurface with that top-hat thingie, are you telling me we can't properly position a couple of shaped charges to shut the damn leak down? You gotta be kidding me.
I've oft been criticized for an overt enthusiasm with and for demolitions. And even in the schoolhouse, I was upbraided numerous times for my robust employment of the P-factor (in demo calcs, P= Plenty. Admittedly, I never came close to Dirty Pat's trademarked, patent-pending "dirty diaper charge," which was a thing of beauty and a work of art).
With the pressure of 5 km of incompressible water up above the leak, I find it hard to believe that there is not a charge array that could shut the fucker down. I mean, BP guys are now pinning their hopes on golf balls and shredded tires, and no one's talking C-4? That's rooty-poot, man.