Define "promptly," then? Because I nkow a few articles I recently finished that use materials only available in one library across the country from me. Will verification of those sources not be prompt enough for someone in, say, Chicago?
It doesn't need to be promptly verifiable by everyone. A TV show that can't be seen legally is not verifiable by anyone. We shouldn't be relying on illegal copies and fansite summaries for our sources.
I wish I could think of a way to make it work - I'm very active in WikiProject Stargate and we use episodes as sources all the time - but a source no-one can access is not verifiable.