Just briefly: because they need to not overheat, can get stuck in places
and killed as a result, can get into places with other dangers (like
electric cords or gas lines -- some ferrets have died under gas stoves
which weren't known to be leaking, or from biting electrical lines in the
walls, and some have taken deadly falls), and because they need water and
food so regularly no ferret should be missing for more than a few hours
if at all possible.
 
Now, granted they may be doing something silly to you instead of really
being missing.  We actually searched outside with a squeak toy (which
they are NOT allowed to play with because of the hazards of latex but
which is useful for calling them to come which they are trained to do
with treats) and contacted all the local vets, shelters and police once
when one wound up playing mobile-hide-and-seek -- for over three hours --
inside our home.  At least HE -- the ferret -- knew we were playing.
When we called back to say "False Alarm" they were all happy about the
good news, too.  Any longer time than a few hours missing should set off
major alarm bells for anyone and begin a search.
 
Serious accidents are not typical.  Most people never have a ferret
seriously injured or killed by accident, though accidents were more
common before a lot of places began providing ferret proofing tips --
places like http://ferretcentral.org, Archives, books, magazines.  When
they do typically they never have an accident happen again.  it is
usually a one time only occurrence, though I guess with enough years
with ferrets (and here I am thinking more in the line of decades) more
would be seen,
 
We have had one accident which was bad enough to cause a hematoma on a
ferret's neck in 23 years with ferrets; she lived.  Our situation is not
atypical.  (She tripped me, and I was injured worse than she was trying
to avoid falling on her as much as possible.)
 
It can be very hard to ferret-proof if a person can't get down on the
floor and look around at ferret height.  Some conditions make it pretty
well impossible.  I've got foot and ankle braces on each side that get me
stuck if I am down unless I have my gardening stool handy or can crawl to
a piece of furniture to get up.  So, I have to ask someone else to do
that for me much of the time.  That's life.  If something as important as
ferret-proofing is needed and if it means asking someone else then that
is just life.  It still has to be done because without it the ferret
would be injured, killed, or get out in which case they likely would die.
 
I've also had to work on teaching the ferrets that my feet are not
particularly safe things, and to not have anything on the floor within
which or under which a ferret may be hiding.
 
They still create some close calls at times, and if I were worse on my
feet I simply would not be able to be safely around them under these same
conditions -- not for their best interests, anyway, and that is what
matters.
 
Everyone with ferrets has to make changes in their lives to protect the
ferrets; that is just a given.  For some of us those changes are harder
to make, but that does not make them less essential.
 
One thing we had considered (but wound up not needing) is sequential
gates so that if I had been stuck with a walker I could have let myself
through the first gate without the ferrets escaping, and then opened the
second gate, collected the ferrets who moved into the between area, and
then gone into the room closing that second gate behind myself and the
ferrets.  Fact of the matter is: if a person has a mobility handicap the
ferrets should never have free run of the home, but instead have large
enough ferret room(s), because even though it isn't PC to say so folks
who have such handicaps -- including me -- simply need that for the
safety of the ferrets and it IS very do-able.
[Posted in FML issue 4623]