Adding another item of things not to do.
at> shutdown -g300 -i6 -y
So I was testing some behavior to see if trying to allocate more swap than the available space would generate the message I was expecting (It does).
My next step was to use mkfile to eat up all but the smallest amount of space in /tmp that I could. Before doing that I set up the at job to try and recover if I ended up in a situation where all of my connections hung.
The result of the whole situation...
I was able to use almost all of my swap, the system was unresponsive for a minute or so while I was filling up /tmp.
While I continued to mess around seeing if normal tool use would also generate the message (It doesn't) I forgot to remove the at job.
So after making a note of my results and writing a message to that effect I remembered that I had an at job... unfortunately about 30 seconds too late to kill the running shutdown.
So much for my uptime.