Hey all (sorry for starting a new thread about this, just subscribed)...
I'd just like to pitch in and say that having a valid hostname is also needed for joining an Active Directory or FreeIPA domain from within Anaconda.
A kerberos computer account principal is created based on the hostname (as in gethostname()) of the machine. The keytab of the machine will contain the hostname too.
So in order to join a domain from the Anaconda UI, we have to have setup a host name before the post install configuration. This means that (for the AD/FreeIPA use case) it's sufficient to have the hostname in the progress 'spoke', as Chris pointed out:
https://www.redhat.com/archives/anaconda-devel-list/2012-December/msg00071.h...
We would theoretically block on prompting for a the hostname if joining a domain.
Somewhat related: In the case of kickstart, we currently assume that the admin has setup some sort of way to distribute unique host names (either via DHCP or munging the kickstart files as they're served). Perhaps this can be fine tuned in the future.
Cheers,
Stef