The Amazon Giveaways program has been running for awhile and in March they service branched out into e-books. It allows authors or publishers to be able to run raffles and prize draws on their blogs on social media accounts and the winners can download the Kindle books directly from Amazon. If you are hoping to get your book more exposure or for your sales ranking to go up, think again.
Kindle Giveaways do not count towards your sales ranking in the Paid Kindle Store OR the Free in Kindle Store if a single giveaway is not claimed. For example, if you orchestrate a raffle draw on your blog and you select 25 winners. If 24 people end up going to Amazon to download their e-book but a single person does not, none of the books count towards the sales ranking.
This situation creates an adverse effect not only on your own download count but also services that track e-book sales. This includes Author Central, Author Earnings, NovelRank and Nielsen.
In order to participate in Kindle Giveaways you need to pay Amazon a fee. I would recommend before you decide to run a promotion on your website or social network, wait for Amazon to fix their system first.