~/.Xresources on OS X
I thought X11 had gone bonkers—I couldn't get it to listen to
~/.Xresources or any variation thereof. It turns out I just needed to install
the X11 SDK (which I did along with all the other SDKs), and things worked
great. I'm guessing the reason is the same reason xrdb didn't work either:
/usr/bin/cpp didn't exist and xrdb failed with a complaint to that effect.