Actually, ED is a Wikipedia fork, much the way the Comixpedia wiki is: it was set up when a number of articles the founders thought important were deleted by VfD.
ED and Uncyclopedia are two forks which benefit Wikipedia in two ways - they provide a place to blow off steam from Wikipedia and they provide a place for all the random Internet shite and bloggerel which may in some way be interesting to someone but is in no way particularly encyclopedic.
-FCYTravis