Apparently Amazon.com is making a move into traditional publishing with their AmazonEncore unit. The first step, described here by Publishers Weekly, seems tentative with a first acquisition of a teen's self-published novel. The PW article gives some insight into their editorial process, but here is Amazon's explanation:

AmazonEncore is a new program whereby Amazon will use information such as customer reviews on Amazon.com to identify exceptional, overlooked books and authors with more potential than their sales may indicate. Amazon will then partner with the authors to re-introduce their books to readers through marketing support and distribution into multiple channels and formats, such as the Amazon.com Books Store, Amazon Kindle Store, Audible.com, and national and independent bookstores via third-party wholesalers.