I'm not an expert in the space, but I'm guessing that graphics cards have only been a non-thin-margin-business for like 5 years. If that's true, the Joel's prediction about graphics cards may even still turn out true on net -- it could still go back and stabilize at low-margin.

That said, I think your overall point isn't affected by my idea. Even a great mind can be wrong occasionally. He doesn't have to be right every time.