Now, that last point surprises me greatly. My assumption (and the prediction of a few SF authors who actually bothered to give it thought) was that the proliferation of recorded media would provide the same kind of anchor to spoken language that widespread literacy had for written language.

Honestly, it's kind of cool that it doesn't. I wonder if languages controlled by central Acadamies, like French, show less linguistic drift?

I HAVE heard that, in the Untidy States, at least, regional accents have started to become less distinct than they used to be because of broadcast media. I've heard a bit of that -- few US-ians of my generation or younger have incomprehensible accents anymore, and people tend to lose their accents (or slip more easily into new ones) when they move to different regions of the country than they once did.