I discovered it when using the zooming function via holding down the Ctrl key and scrolling the mouse wheel to make the display more visible to the group I was demo-ing to. Moving the WebDialogWindow around leaves text behind. Oops.
Not exactly the demo I was shooting for.
But can be used to generate some cool effects:
This is what the WebDialogWindow looks like before moving it:
These are screenshots of the WebDialogWindow on zoom:
Floating away:
Where did my window go?
An out of body experience: 
And my personal favorite -
WebDialogWindow Abstraction : 
