This initially appeared on Postlib.com.
We usually underestimate the time and cost required to bring a predicted innovation or technology about (this is probably equally true of our personal lives as well as on a grand scale).
But when that innovation or technology does arrive, we usually find ourselves having underestimated its impact, power, or effect.
We usually underestimate both:
The time and cost required to bring a technology or innovation about.
The eventual impact, effect, and manifestation of that technology or innovation when it's finally achieved.
I think the formulation above improves on the following widely known and oft-cited quip:
For starters, technology is often over-hyped, plateaus, then collapses into mass disillusionment, despair, disappointment, and failure. (Occasionally such technologies rebound and go on to overcome their flaws: credit cards, the first cell phones, and so on were all examples of that).