Effects of mounting / (filesystem root) with nodev option

I’m wondering about the effects of setting the nodev option for / mount in /etc/fstab.

As I understand it, nodev prevents the interpretation of special nodes, so you can prevent rogue users or attackers mounting and using their own device nodes to wreck havoc on the system.

My first thought was that mounting / with nodev would render /dev completely useless and prevent the system from starting up properly because no devices (including the partitions mounted on /home and /usr) could be used.

So, imagine my surprise when I tested it out on an Ubuntu installation and everything appeared to work as normal. /dev/zero and /dev/null did what they were supposed to. I didn’t have other device nodes that I could do anything with, such as sockets, but not that I know what to do with them anyway.

1. Can anyone explain what happened, and why the installation continued to work?

2. Does the system implicity ignore stupid things like mounting / with nodev? For that matter, is the handling consistent across different distributions or kernels?

3. And back to the original question: Are there actually (ill) effects that I did not manage to observe/trigger?