In Gnome 2, you could set the mouse pointer to enlarge briefly when you pressed the Control key. This was nice because sometimes when you've just come back from the screensaver or dropped the mouse, you might not know just where on your desktop the mouse pointer is. Tapping the Control key and seeing the pointer expand into a fairly big circle for a second or two is much easier than waving the mouse itself around until you locate it. I'd appreciate it if the XFCE devs would consider adding this to version 4.10, and I'd be very surprised if I were the only one who'd like it.
This is not a bug in xfdesktop or even related to it.