For what it's worth, I first heard that analogy -- more precisely,
"never understimate the bandwidth of a station wagon full of mag tapes
going up the Taconic Parkway" in the 1969-1970 academic year. At the
time, IBM had a small research lab across the street from Columbia
University; I worked there as a systems programmer for an IBM 1130. One
of the major purposes of this machine was to act as an RJE (remote job
entry) station for some big mainframes at Yorktown Heights; when we
were having trouble getting it working, someone uttered -- more likely,
quoted -- that line. This is considerably earlier than the Tanenbaum
story, though well after the invention of early modems. (For what it's
worth, the modem we were using was probably 2000 or 2400 bps,
half-duplex; the link used bisync. And it was BIG.)
--Steve Bellovin, http://www.research.att.com/~smb