We haven't explored the Kindle Singles world as much as we'd like. How does a person hear about a Single? How does one of them catch fire and become a big selle

We haven't explored the Kindle Singles world as much as we'd like. How does a person hear about a Single? How does one of them catch fire and become a big seller? Is it up to the author to promote them, or are there websites/periodicals/Twitter feeds/whatever that have a lot of influence on sales?