Though he notes that his armored car quip is approaching 20 years old, dating back to the dark days of Windows 95. Perhaps the better way to think about it is: encryption is necessary but not sufficient. If the NSA has extruded its tentacles into sufficient endpoints (operating systems? firmware? antivirus software?) that's a problem that encryption won't by itself solve.
Hey, I'm channeling RMS: free software is the real solution! Unless the NSA's tentacles extend to the compiler you use to compile the free software. :)
(Lather. Rinse. Repeat.)