I've put the following into my keyboard.xml file (
$HOME/.xbmc/userdata/keymaps/keyboard.xml) to disable the "power" button on my MCE remote control. Prior to this change, when I'd change "Activity" modes on my remote control (Harmony 650) it would send a power toggle that would cause XBMC to exit.
Previously I had a hack of binding the button to a different code. Today I learned about the NOOP binding from the friendly team at the XBMC booth at SCALE11x today. Thanks!
<keymap> <global> <remote> <power>NOOP</power> </remote> </global> </keymap>