Dean's Certification Letters

Ok, what is the deal with these? I know I'm supposed to be answering the questions and not asking them, but they just started really appearing on the scene a few years ago and schools are incredibly inconsistent about what they mean by them, when you need one, whether or not there's a form, who should fill it out, etc. I thought I'd open this up and just let everyone share about their lovely Dean's Cert Letter experiences, any feelings you have about them, anything you've learned about what certain schools mean when they ask for one, etc. Have a good time.
(This is an experiment in my blogging career... Let's see what happens! Besides, I don't have time to keep answering all of these wonderful comments so have fun answering each other!!! I look forward to reading them myself)