I don't know. Somehow getting backstory on characters (which effectively destroys all existing fanfiction on such a character) without getting a book to go with it is like receiving a package that consists only of its wrapping. Nice as a concept, but somehow completely without the satisfaction that comes with unwrapping and exploring what's inside.
As it is, pottermore tells us a lot of things we already know, allows for random clicking and searching of items, the most boring occupation imaginable, even if you're just eight or nine years old, and every now and then we get a self-indulging post along the lines of: "This is what I thought when making up the name XY: Nothing! It just popped into my head! Surprise!!!" or (worse) "See this minor character, who, up until now, provided good opportunity for the less heterocentric-minded people who wanted to deal less with stereotypes and more with character depth to write fanfiction about them? Watch me attach a random backstory to them without also giving you an actual plotline to enjoy, effectively destroying all (or most of) the character's potential and adding nothing in terms of literary enjoyment."
Gna. Frustrating, somehow, especially since nothing in the world will stop the fans from going with this, not matter how pointless it may seem.