There is a bug in the new e-mail filtering so that too much is filtered.
It is tracked in http://bugzilla.mozilla.org/show_bug.cgi?id=71611
If you filter cc changes, you won't receive mails about changes to a bug
regardless of how much is changed in the bug if someone changed the cc
at the same time. (common case)
The workaround until the Bugzilla gods have fixed the bug is to turn off
e-mail filtering or avoid changes to CC when you change something else
that might be interesting to someone.
/Daniel
