Just a note.
My brother told me that if a dwarf for some reason falls over (cavein, swallowman attack, whatever) in a flight of stairs he falls down the stairs to the bottom. I don't know if this applies to if he just falls asleep in it but if you make one huge staircase that might be something to look out for... and a reason to make a huge friggin staircase. In fact I have a pretty large staircase I'll tell a recruit to go stand at the top. brb.
EDIT: nope. falling asleep didn't cause him to fall. so I caused a small cave-in next to the staircase. of course I forgot the fact that this isn't a pit it is a constructed tower and the piece of roof on the top level (6) caused a chain reaction that collapsed floors BUSY with dwarves all the way down to level -2.
Apart from the recruit participating in the experiment 2 children, 2 soldiers and 5 animals fell into the hole. Broken arms, hands and legs aside all the dwarves will survive... except the guy who fell from the top floor.
These are his mangled bodyparts: upper body, the entire left arm, the entire right arm, both upper legs, left foot, left lung, left shoulder, upper spine. Everything else is bruised or broken. It'll be interesting to see how long he survives. oh and he's a bit unhappy too.
Could be worse I guess. Now all those who got hurt fell down the hole, there are 7 stunned dwarves and animals at the bottom of the staircase but not a single one anywhere in the middle of it.
Conclusion: Tall staircases are dangerous but large holes are much more dangerous!
... now I have some repairing to do.
EDIT:
apparently I have some burials to attend to as well. Children can't take much of a beating ...