Curious as to whether or not my little book stood a chance of being accepted by Kindle Singles, I did a little digging around on the Amazon Kindle Singles site. Since it's launch in January of 2011, Kindle Singles has published 3 new titles each week. Their editor received around 50 unsolicited submissions each week, so Dave Blum's job leaves knee deep in manuscripts every day. Most of the lucky ones who are chosen to live on this list of Kindle Singles are exclusive to Amazon, meaning this is mostly original material. Others accepted come from traditional publishers and also e-singles publishers The Atavist and Byliner. More about those sites later.
Most authors covet the Kindle Singles list over the Barnes & Noble Nook Snaps and Apple QuickReads because they receive more marketing and promotion help from Amazon. Also, you've got to admit most people use Amazon not only for book shopping but for looking up info on a book in mind. It's like a library helper site as well as a book seller.
So in a nutshell the answer to the question "Who gets published on Kindle Singles?" is the lucky ones. Also, I've got to admit the talented ones. So I guess even if you do have a flashy book cover, it's still not going to fly with Kindle Singles because they are looking for quality; not just bling.