DITYIWAHP is right about the time delays being very important too. In fact, on the Harrier, in the hover, the delay due to human reaction time is so critical that the advice used to be to eject immediately if there was any red warning caption. It may have been a harmless OXY caption, but in the around-a-second it took to look in and read an OIL caption or similar major engine problem, the aircraft would have built up enough sink rate to kill you, ejection or not.
In the Air Defence world, the sink rate calculation means that if are doing a 'post-hole' manoevre in air combat, going straight down supersonic, you are pretty much stuffed if you don't start recovery by 10,000 ft, as even the seat can't save you. Definitely not zero-zero.