(FORTUNE Magazine) – Sure, the information superhighway sounds as inevitable as it does alluring. But don't count your bandwidths before they're wired. Modern industrial history is littered with technological revolutions that took unexpected directions, took longer than predicted, or cost more than anyone imagined. Some prominent corpses:

-- ROBOTS. When, in 1939, Westinghouse produced a robotic man, Electro, and his robot dog, Sparko, that could ''talk, see, smell, count, and sing'' to audiences at the New York World's Fair, it looked as if personal robots might be for real. By the 1950s, pundits were predicting these rascals would be so ubiquitous that humans would work only ten hours a week. Are you?

-- THE ATOMIC AGE. In the 1950s atom power was going to be the power ''too cheap to meter.'' Engineers predicted that pellets of plutonium would power homes, refrigerators, wristwatches, trains, planes, and automobiles. In 1958, Ford Motor Co. got a jump on the impending atomic age by making a model car with sweeping tail fins called the Nucleon. Its imaginary power plant: a portable, rechargeable, nuclear reactor. Such aspirations ended when Americans developed a severe -- and seemingly permanent -- case of nuclear anxiety.

-- ULTRASONICS. Ultrasound has established itself in some marvelous niches, such as cleaning jewelry, moisturizing the air in infant nurseries, and producing those hideously ugly (yet wildly exhilarating for parents) sonogram pictures of babies in utero. But the future-gazers of 25 years ago anticipated much more. They foresaw ultrasonic dishwashers, washing machines, and showers. What sonophiles failed to anticipate is that no one would prefer sound waves beating dirt from his body in dusty clouds to having hot, steamy, skin- tingling water scrub it off his back.

-- A PLANE IN EVERY GARAGE. A House of the Future at the 1933 World's Fair in Chicago contained on its first floor a recreation room, a garage -- and a hangar for the family plane. ''People thought this technology would trickle down when a Henry Ford of flight devised a way to make safe, inexpensive personal aircraft,'' says Joseph Corn, professor of American history at Stanford University. While the Ford of personal flight never appeared, technology did in the end make it affordable for almost anyone to fly -- provided Everyperson is willing to squeeze into a skoonched-up seat in what usually feels like a cattle car.

As for the electronic highway, remember teletext, video phones, and quadraphonic sound, among other things? All became road kill on this future freeway because they have failed (so far) to develop viable markets. Timing, after all, is critical. In the mid-1940s science fiction writer Arthur C. Clarke foresaw the possibility of constructing a global communications network based on satellites in geosynchronous orbit. But had anyone tried to carry out Clarke's vision before the 1960s, he almost certainly would have failed -- because Clarke did not foresee the semiconductor revolution that makes today's satellites possible. The satellites he envisioned were occupied, like lighthouses of old, by a tender who stood ready to replace burned-out vacuum tubes. Wonder why he didn't think of robots?