Older releases didn't have NameVirtualHost in ports.conf, but I think that was before 8.04.
# If you just change the port or add more ports here, you will likely also
# have to change the VirtualHost statement in
# This is also true if you have upgraded from before 2.2.9-3 (i.e. from
# Debian etch). See /usr/share/doc/apache2.2-common/NEWS.Debian.gz and
# SSL name based virtual hosts are not yet supported, therefore no
# NameVirtualHost statement here