April,
 
I've noticed the same thing.  Bottle brush tail.  Actually, I don't think
it has anything at all to do with them being annoyed.  Quite the opposite
in fact.  One of my girls will even poof her tail just from being petted,
if she's really in the mood.
 
Any of them are prone to bottle brush tail when I scritch them in a
particularly good spot at a particularly good time.  And they ALL poof
them out while playing.  It seems to me it is a symptom of pure
enjoyment.  And she probably war danced down the hall because you
stopped, not because you scritched. ;-)
 
These days, if I see a bottle brush tail, I know I'm doing something
right, and I better not stop unless I want a pissed off weasel on my
hands.
 
Melissa Kuzara
Mira, Robin, Samurai, Nietsche and O'Dell
Missing Cael, Booboo and Tasha always
[Posted in FML issue 3924]