Because the Organizer is still the Organizer - Outlook kind of loses the
'from' concept with meetings, they don't behave quite like other emails.

Beware of forwarding meetings though, it does tend to confuse things - see
http://office.microsoft.com/en-gb/help/HA011276781033.aspx for a good guide
to Calendar best practise.  Follow the tips there, and you'll avoid the most
common causes of problems with appointments.