Our ferret, Mortimer, sprays more than is usually polite in mixed (mustelid
and non-mustelid) company.  We got him and had him neutered at Christmas
time.  Since then, he's improved dramatically, but still sprays every once
in a while.  I'd say three times a week.  It didn't seem to be related to
fear at first, but now I've made what I think is a useful observation.
 
Mortimer is kind of a chicken.  He's well loved, and not fearful, but easily
startled.  He will spray during a rough and tumble play session with us or
his ferret bother, sometimes he sprays if he hears a loud noise (concurrent
with running under a piece of furniture), I saw him spray once when I
playfully tossed him on a bed (no injury, lots of stink), and I think he
occasionally sprays if he's roused from a sound sleep.
 
We've pretty much decided we can live with it rather than put him through
the discomfort of descenting (not to mention the expense!) The smell
dissipates rapidly.  Burning a candle in the afflicted room helps.  (Take
appropriate ferret precautions) And I think if you're observant, the
spraying gives you insight into what's going on in your critter's head.
 
If you decide to have him descented, no one would fault you.  Some ferrets
just can't handle having scent glands.  :)
 
-Catherine Shaffer
[Posted in FML issue 1533]