Alright, so... I haven't mentioned it up until now because I didn't feel it would have any bearing on the problem, but the installation in question is a VirtualBox guest operating system running on a Windows host.
Since I didn't have any particular attachment to the installation, I decided to fdisk and start from scratch. I did this and got the barest most basic Gentoo installation up and running. After I had done this, I realized that I had forgotten to add net.eth0 to default. I did so, rebooted, and sure enough, net.eth0 did not start. I then went and meditated under a tree for a while, because it seemed the world had finally turned its back on me. After this, I said 'what the hell' and tried out a few things. One of the things I tried was to rebuild openrc. For whatever reason, this worked. I'm going to try this on another installation of VirtualBox on another machine and try to reproduce it, but I'm still a little in the dark. This installation was built using the latest minimal install iso, latest stage3 and latest portage snapshot.
