Comment #7 on issue 492 by esteba...(a)gmail.com: Glamour browsers do not
release all subscriptions to announcer objects
http://code.google.com/p/moose-technology/issues/detail?id=492
GLMUpdateAction is getting into the announcement because you do:
in registerInPresentatio:
...announcerObject
on: self announcement
do: [ ... ]
then, the block is registered, and the way you can later unsubscribe is by
using the BlockClosure>>receiver... which is the GLMUpdateAction object :)