Kindle Worlds sounds like another of Amazon Publishing's ingenious inroads to collecting revenues on IP f/k/a publishers' profits:
"We will also give the World Licensor a license to use your new elements and incorporate them into other works without further compensation to you." (Why should Amazon own an author's original character?)
"This isn't Amazon figuring out how to make money off fan fiction; this is Amazon entering into a partnership with media properties to crowdsource officially licensed novelizations."
-- Malinda Lo, "
Amazon Tries to Monetize Fan Fiction"
In the more selfish sense, what I mind as a consumer is the idea of massive numbers of fanfic books appearing in every bookstore-wide search -- searches which, in my experience, tend to be weighed down with irrelevant results already.
I'd be far more open to the idea if fanfic were only included in searches at the user's prompting.
Like the Kindles I've used, the Amazon Store isn't the best at displaying specific lists of the kinds of books I want -- mostly because it never stops pitching the many it wants me to buy as opposed to the few I might actually want to own.