Oh I can see the pros getting screwed on this deal. Why pay a pro when the fanficcers will do it for free.
Because experienced professionals will turn out better work than most of the amateurs and thus their work will sell better?
Quality of work aside, why pay a higher amount to a professional when you can pay zero to a fanficcer and make pure profit? You can bet the royalty scheme on Kindle Worlds is going to be IP holder weighted.
Why pay 1 person out of my pocket, when I can get a dozen little monkeys working for me for free and all I have to do is cash the check coming in?
Not saying it'll be the death of professional tie-in writers, but it's has the potential to cut into their bottom line and clog the market.