I've noticed a couple of people asking about this mix of pets. We have
introduced four ferrets into a home with two cats over a period of about three
years. (One male cat about 8 years old and one female cat about 5 years old.
Both cats are "indoor only" animals from an animal rescue so both have only
vague hunting memories if any.) My personal advise is to maintain a healthy
distrust of the relationship and don't leave them unattended. Following are my
observations.
 
The ferrets will approach a stationary cats, get down on their belly when
within 6 inches and inch forward till touching the cat if possible. This annoys
the cat intensly and delights the ferret! The cat will generally get up and try
and walk away. Occasionally the cat will stand and hit at the ferret with its
paw. (Typical two or three rapid fire swipes.) The ferret then tries to get
under the cats belly and make like its going to nip the under belly. Eventually
the cat retreats. Very rarely does the ferret retreat.
 
I've also seen the cat approach ferrets which are playing in a plastic bag.
(The cats also normally like to play with plastic bags.) The result of this
is usually a territorial struggle for who owns the bag. The cat generally
wins. The biggest problem here is that the cats seem far more willing to be
agressive when the ferret is inside the bag and can't be seen.
 
Bottom line: We've seen no mishaps in three years. We allow all animals free
run while we are in attendance, typically if we are sitting down or playing
with them. If the ferrets are out and we are busy with other things we
generally put the cats in another room (usually they go and sleep on the bed,
the bedroom is not ferret proofed).
 
============
FYI:  Do your ferrets chew power cords? (nod "yes" now!) I finally found a fix.
Get some 1/4" diameter clear plastic pipe such as is used for water conditioner
overflow pipe. Run the power cord thru it, replacing the plug on the end. They
still chew at the plastic pipe but its too solid for them to break thru. The
pipe, being clear and only a 1/4" diameter, is not too unsightly and is
definitely not as unsightly as a fried ferret.
[Posted in FML issue 1221]