During installation of Fedora 18 Alpha, the network configuration files /etc/sysconfig/network and /etc/sysconfig/network-scripts/ifcfg-XXX are not written. Even if these files do not exist, the resulting installation is querying IP information via DHCP, but the hostname is always set to localhost.
I think this is fixed post-alpha, but reassigning for a double check.
*** This bug has been marked as a duplicate of bug 853584 ***