According to today's
"Ask the Judge" corner on Starcity Games, Memnarch can only interfere with the Worldgorger Dragon Loop if Memnarch steals both the animating enchantment and the Dragon.
However, doesn't stealing the enchantment stop the loop (the repeated process of the dragon bouncing from the graveyard to play and back)? If I steal the animating enchantment, doesn't the opponent end up with a lonely Worldgorger in play?