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.