Web sites of all kinds love (and need) to build their brand and audience by engaging them in various ways. One traditional method that has been taking a pummeling recently is the "comments" section. Lacking the will or the wherewithal to moderate or respond to comments, many sites are blocking comments and relying on Social Media to pick up the slack by proxy.
TechDirtBy outsourcing all conversation to Facebook, you're not really engaging in your readers, you're herding them to a homogonized, noisy pasture where they're no longer your problem. In short, we want you to comment -- we just want you to comment privately or someplace else so our errors aren't quite so painfully highlighted and we no longer have to try to engage you publicly. All for the sake of building deeper relationships, of course.