I'm using Ubuntu 12.04 with Unity, which I suppose uses Compiz as well. I have Compiz Settings Manager, and make the top left and bottom left corners of my screen activate the "Scale" (like Exposé) function to scale and show all windows.
The problem is that when I restart the computer, the hot corners no longer do anything. I have to go back into compiz settings manager, delete the hot corner option, and then set it again. Something seems to be overriding or deleting the compiz hot corner setting on restart.
Update: Sometimes, the setting loses its footing even while the computer is running. I haven't figured out yet what triggers it.
Best Answer
Main bug reports are at https://bugs.launchpad.net/ubuntu/+source/compiz/+bug/986208 and https://bugs.launchpad.net/ubuntu/+source/compiz/+bug/858845.
For 12.04
Semi-Permanent solution copied here:
active_plugins
I say "semi-permanent" because some software updates (Unity) may cause the plug-in order to get rearranged, so you may need to repeat these steps 2 or 3 times per month.
For 12.10 and 13.04:
The above fix stopped working with the upgrade to 12.10 and continues on with 13.04. There are proposed solutions for 12.10 & 13.04 at the bug report link above, but so far nothing solid.
Semi-Permanent solution for 12.10:
active-plugins
Note that system updates may revert this fix and you may have to use dconf to fix it again.
Please continue to contribute to the bug report to get the problem fixed in 12.04 LTS, 12.10 and beyond.