Made a short animation - added in a face effect - rendered it and played it - NO ace appeared. Tried several different faces (different sets of images) - none worked. They do show up if I put them on as an image.
So to be sure it wan't a data transmission error - I moved the face over to start at 5-seconds in and place a 5-second butterfly effect ahead of the face. It played the butterfly (of course in debug it was not smooth - but it played it all).
Just as an aside - you might recall in the other thread about the exporting of clipboards and avis - it was the faces sect that was missing from my avi exports, too. Makes me wonder if there is some correlation between the two events.