Dear lazyweb,
Which part of acpid is it that sends XF86Display key events to my X server? It's broken: when I suspend and then resume, it keeps sending those events over and over in an infinite loop; and since the script that I've hooked to that event takes an order of magnitude longer to run than the interval between said events, I'll just say that I find this highly annoying. I'm quite sure it's actually acpid that's sending them out, since the fix for this problem seems to be to call sudo /etc/init.d/acpid restart...
Occasionally, I don't think the ACPI daemon should be sending out these events at all (it seems to do so whenever I open or close my laptop's lid), but that's a different story...
I had the same problem and found a fix:
sudo touch /var/lock/acpid