When a high value is entered into the Camera Distance field in the 3D Effects 
dialog, subsequent values result in distorted shapes.

To reveal this distortion:
 1.  Open a new presentation document.
 2.  Select the 3D Object tool.
 3.  Draw a simple cube that takes up roughly a 1x1" area on the page.
 4.  Right-click on that cube and select 3D Effects.
 5.  Select the Shading tab and click in the Camera Distance field.
 6.  Type 0.04 and click Assign.
 7.  Exit the 3D Effects dialog.
 8.  Repeat steps 2 and 3 to draw a similar cube near the first.
 9.  Right-click on that cube and select 3D Effects, select the Shading tab, 
and click in the Camera Distance field.
10.  Enter 8,000 and click Assign.

The dimensions of the second cube are noticeably different than the first.  If 
they are not apparent to you, try 10,000 instead of 8,000.  On my computer, 
specifically, the cube was "squished".  The distortions get more spectacular 
the higher the Camera Distance value.  This bug is significant if, say the 
user accidentally enters 30000 instead of 300, then tries to correct it.  
Their object will be distorted beyond repair.