Earlier quoted context omitted.
http://www.forbes.com/sites/kashmirhill/2013/07/24/blueprint...
Very interesting. The tl;dr seems to be: nobody knows for sure, but yes... it could totally be used for full content storage for some length of time.
Now somebody here claims it's around 1e7 B compressed for an hour of phone talk (not transcribed only compressed). That gives 2e10 hours stored. Storing it for 2e8 Americans there's space for 100 hours per person. But they also want the world, not only Americans.