Selecting multiple folders on the desktop and dragging to the right overlaps them all
If there are a number of folders on the desktop arranged in a vertical series and then they are dragged to the right of the desktop screen for extra space; if dragged too far to the right they all become over lapped.
There margin for this to occur is slight, as I have tried it a few times to reproduce. When selecting folders a perforated edge can be seen and while dragging them over to the right if this edge only slightly moves off the screen, folders are grouped over each other.
This is possible in unity-2d also.
I'm using Ubuntu 12.04 lts, and the display is a 1280 x 800 laptop screen