Binary package hint: compiz
If you have a maximized Firefox window, throwing your mouse to the right usually lets you scroll, due to Fitt's law. However, with compiz or beryl enabled, it breaks Fitt's law because for some reason it reserves a pixel of space on the full right and left edges of the screen (not just the corner four hot spots that it uses for Expose-like stuff).
Also, if you have your panel oriented to the left or right, you run into this same problem, where you can't access menus by throwing your mouse to where the menu is; compiz again reserves space along the full length of the left/right edges of the screen.
I usually use my web browser in an unmaximized state but move it so that the scrollbar is just falling off the edge of the screen, so that I can flick my mouse to the right and use the scroll bar easily. This works in all OS's window managers, from OS X to XP to Fluxbox to Gnome and KDE.
However, with compiz enabled, moving my mouse to the very left or right of the screen (for scrollbars) makes it look like it's not focusing on the object. I think this has something to do with how AIGLX reserves space outside the desktop for buffering, or something like that.
This doesn't affect the top or corners of the screen however (plus the corners are reserved for things like Expose, which is fine)--only the left and right edges with compiz don't obey Fitt's law.
Forwarding an event from one top-level window to another is not possible. I
could send a fake event using XSendEvent that match the edge window event but
there's no guarantee that this will be handled correctly by the application.
Considering that the pointer isn't actually in the application window, such a
fake event might just be confusing for the application.