I have my flashing bell set to just the window titlebar. When, for example, I
cat a binary file, I hear a bunch of beeps, but the flashing titlebar gets
rate-limited. However, if no window has the focus, or the focused window is a
desktop or a menu, it switches to full-screen bell. (Aside: would it be possible
to flash the window that requested the bell instead of the current window?)

Try it out: Turn on visual bell and then say sleep 1; python -c "print chr(7) *
50" and focus the desktop. You get a whole bunch of annoying flashes.

In short: the fullscreen flash should be rate-limited just like the titlebar flash.