On Wed, 22 Feb 2012 03:20:52 -0800 (PST), Man at B&Q wrote:

There is another problem here, namely that if a much higher
density
portable energy solution was developed it would have too much
potential
to be "unsafe".

You mean like a tankful of petrol or diesel?

Tanks of petrol are nasty, the vapour produced at normal temperatures
will burn (explode) with a tiny source of ignition. Diesel has to be
got fairly hot before it vapourises enough to catch fire. Starting
from cold it doesn't even burn well on a wick of some sort. Biggest
danger from a diesel spill is slipping on it rather than fire.

--
Cheers
Dave.