This is a proposal for a new "Compact Window" mode or "Folder compacting"
command in spatial nautilus, and its intended to minimize the need of manually
resizing nautilus windows for advanced users (in other words this is an optional
behaviour, not the default).

Lets says I downloaded amode for experts dozen images into my "Downloads" folder
and I want to move them to my "Pictures" folder. When I open "Downloads" I will
resize the window (if needed) to be able to select all the images I want to
move. After moving them to the "Pictures" folder, the "Downloads" window will
show a window with a lot of empty space. Since spatial nautilus remember the
size/position of the windows, I'll have manually resize it (by dragging the the
corner/border etc) before closing it, or leave like that (which means I'll have
to resize it the next time I opened it).  

What I want is to be able to compact (automatically or by a keybord shortcut)
the window so that there is no empty space visible. 

IMO, this combined with window tile/cascading in the window manager could
improve nautilus usability for expert users without changing the spatial metaphor.