i18n message factory in zope domain

Hi,
    Should we create separate message factory in 'zope' domain for
each packages ? If so, can anyone explain why it should be like that.

Few weeks back a new message factory is created in
zope.i18nmessageid [1] .  And now some packages use this directly.

I am bit confused now ...

[1] http://svn.zope.org/?rev=80022&view=rev


Regards,
Baiju M