Wow, that is in my opinion an amazing development and only possible with today's technology like Kindle and other ereaders.
It wouldn't be worth it to publish fan fiction books just to see if they sell, but it doesn't cost much if anything to publish an ebook. For the first time fan fiction writers have an opportunity to make some cash off of their stories, and the original authors make more revenue without lifting a finger. Seems like a win win situation to me.