Jeff,
  are there any accidents you've seen where this might have saved the
occupants?   Probably hard to tell when the fire burns the entire airplane

In small aircraft accidents involving a fire the fuel cell is often breached and the fuel is splashed on a hot engine. In some cases where the engine is cold prior to ground contact there is no source of ignition and therefore no fire. Brent poses the extreme measures that must be taken in a IV P to isolate the fuel.

 

In many cases the occupant is too stunned/ injured/ rendered unable to get out of the cabin. I would put my money in better restraints/ airbags.

 

Jeff