Comment 41 for bug 78538

(In reply to comment #33)
> I believe it will lead to more confusion as people keep trying to
> open windows and firefox "silently" does nothing. They might not realize the
> window is opening on the other screen.

Metacity will move the FF window to the current workspace if you click a link in thunderbird or gnome-terminal. And compiz will switch the workspace to the one where the FF window is. I don't know how the other WMs behave, but it seems like FF does its best to make itself visible after you open a link and the window isn't in the current workspace.