Might I add, the sales conversions directly resulting from the "30 day money back guarantee" banner (displayed at the bottom of most our site pages) is a difficult metric to track.

We've linked the banner to a page informing users of the policy and we track the "Viewed refund > Checked out" event in Kissmetrics. In the last 30 days that was around 10% of the visitors.

That said, most people simply view the banner on the product listing, and I'm quite certain that gives them assurance and confidence to complete the order. We definitely have seen an increase in sales since introducing the refund policy, but others vairables have also been at play.