Staring blankly at the screen.
Should the Register be blocked, I doubt that every person in the known world with an internet connection would immediately twig that it had happened. The supposition that users would be unaware of services being removed quite rightly takes into account people who do not currently use their service.
I think that this ruling suggests that not everyone is acutely aware of every service that is being throttled or to what extent given that the majority of people don't access the majority of the content available.
If the iTunes store went offline tomorrow then I'd never know.