The earliest steam-powered car that we know of was built in 1769 by the French inventor Nicolas Cugnot, seven years before the American Revolution. It had three wheels and moved about as fast as a man could walk. It was intended to pull canons.
In both cases, there was a huge gap between what we would today call the "proof of concept" and the first commercial introduction of the product. While we certainly wouldn't claim that this indicates that the first Model Ts could have been rolling off the assembly line before the Civil War, if only they had gotten their act together, or that television, rather than radio, might have been the mass medium of the Depression, this does suggest that there was an opportunity gap---that some enterprising group of scientists and engineers could have introduced these products earlier, and been awarded the benefits that are often concomitant with such a head start.
From a technological perspective, it seems safe to say that 1885 is not the absolute cut-off date for when the first commercial cars could have been built, or that prior to the mid-1940s television had to be merely a hobbyist's novelty. We could go on with further examples (the insistence of the learned that heavier-than-air flight, or rocket flight, or what-have-you, was either simply not scientifically possible or possible but not to the point of practicality), but the poor track record of such nay-sayers is widely enough available to make further embellishment unnecessary.
Assuming these same dynamics are still in play---and there is no reason to suggest that they are not----what does this mean for us today? What is the automotive technology or broadcast technology just waiting to be taken advantage of that won't be heard from for another five or ten or twenty years---rather than today---just because no one has thought to do it, or done it correctly?
What product opportunities or technologies are we failing to exploit as a result of following the defeatist (but oft-heard) mantra, "well, if there were any value to that, someone would already be doing it." As the above examples show, there often is a gap between the technology reaching usefulness and the "someone doing it." Indeed, if one had taken the advice of Siegfried Markus, one of the automobile's early innovators (and who should know better?) that pursuing the development of the auto was a waste of time, even in the Twenty-First Century our streets might still be packed with horses, and all that comes with them.
It’s hard to imagine any significant portion of the American economy today being devoted to cotton oil, cattle feeding, or leather. Even those industries from 1896 which still exist today make up only a small portion of the American economy (a quick perusal of the thirty components making up today's Dow should convince you that, with the exception of General Electric, there is very little overlap between today's economy and that of 1896---and even General Electric left the kerosene lantern business a while ago).
Yet, if we had looked at the economy of the time and the technology of the time, where would we have focused our research: less dangerous kerosene lanterns, cleaner burning home coal furnaces, more efficient leather curing. Some of the major technologies of the next few decades, even though already on the horizon, would have been ignored. In 1906, the year of the first extended broadcast of the human voice, research into more efficient telegraphy (i.e., better Morse code) would still have seemed a good investment---yet less than twenty years later, Radio Corporation of America's earnings were at $2.5 million (in 1925 dollars!). By 1928 its earnings were $20 million. Its stock rose accordingly, from 1.5 in 1921 to 549 in 1929 (granted, subsequent economic conditions did have a negative impact, but the basic idea is clear---even at the height of the Depression radio was, of course, a central fixture of American life, the internet of its time).
None of this is to suggest that every technological possibility or research project will result in an economic return---or even that most of them will. But putting ourselves in the position of, say, someone living at the turn of the last century but possessing contemporary knowledge---or someone living today but possessing knowledge from fifty or a hundred years in the future---is an invaluable thought experiment. The question to be constantly asking ourselves is: what technology from the year 2010, or 2025, could we be selling right now? What technological opportunities are sitting in front of us at this moment that, due to a failure of imagination, or of nerve, we are not seeing?