compiz should not default to using screen corners
Description of the problem:
The corners of the screen are already being used on a default Ubuntu GNOME install so compiz should not default its effects to them.
Fitts law says that the corners are a good place to position things (infinitely deep in two dimensions - can't overshoot because the pointer becomes "trapped") and it seems that Ubuntu has taken that to heart by placing things in each of the four corners of the screen (from the top left going clockwise: main menu, log off button, recycle bin, minimize all/show desktop).
A default install of compiz on Edgy has set up various effects on these corners too, which conflicts with the buttons already there (e.g. I go to hit the log off button and wind up activating scale windows instead). The only feature that could possibly be set as default is the show desktop feature in the bottom left (as this is serving a very similar purpose to the show desktop button).