What an awesome image, KC. The Hubble continues to amaze. I'm so glad that our manned spaceflight program managed to both repair and update the telescope before the premature end of our ability to even get to the ISS, much less reach the Hubble.
As others have mentioned, it's the angular momentum in the system (which comes from the fact that gravitational interactions from surrounding mass are not perfectly spherically symmetrical) that causes the flatness. I think a very useful thing to picture is what happens to a blob of pizza dough when you start spinning it; regardless of the initial shape, it always ends up mostly flat and round.
Andromedia Galaxy (sharpest ever view)...just released...very big image, takes a bit to refocus when you zoom in a level. Absolutely stunning! Seeing the seemingly endless number of stars...I know there's a quarterback for the Texans somewhere out there. http://www.spacetelescope.org/images/heic1502a/zoomable/
