Found this a few different places:
Cory Doctorow on NPR's brutally stupid linking policy: "NPR joins KPMG and other bastions of cluelessness by requiring that anyone who wishes to link to the NPR site fill in this form. No matter how deep or shallow your link is, NPR requires you to fill in this form." [From the Desktop of Dane Carlson]
I went and looked around the NPR site at random story pages and didn't notice anything on any of those pages about not linking. So I guess it must be hidden someplace or you're just supposed to know. I really would like to know why they felt it was necessary to do this.