If you follow the URL on the certificate (www.mydeltarewards.com) it takes you to a redemption website. The site doesn't have any content on the landing page, but there is a mailto link if you have trouble -- that connects to an e-mail address at diamondh.com. DiamondH is a vendor that provides employee recognition programs. If you go there, you can download a case study on Delta. While the case study is short on content, it does mention how Delta has several recognition programs they've implemented.

I can't imagine how many points you need to redeem for merchandise. I would expect that the majority of Diamonds never redeem a single certificate (don't have one at the time, don't care, don't remember, etc.), so that takes a lot of the possible points out of play. But to make it worthwhile, it's not about just pleasing one customer, so I would think you'd need at least a few certs to score an ipod.