If anything of consequence occurs in this era of smartphones and multi-G wireless networks, a horde of "citizen journalists" will doubtless be on hand to capture and broadcast the sights and sounds.

Still, it was not until 1975 that Geraldo—yes, that Geraldo, Geraldo Rivera got hold of a copy of the uncut Zapruder film and played it for a national audience on his show, “Good Night America.” Which ...