I am not sure why so much space. My screen http://dl.dropbox.com/u/1522294/Bar_space.jpg
does not have much space at the right end of toolbars. I do have "Enable customizable toolbars" checked in preferences.
It does remind me of a time when I was testing some new button on a toolbar. I had forgotten to put the bmp file for button into the skin. The macro ran and made a place for the button. Since there was no bmp file with the button picture, the space was left blank.
Hope this is of some help.