Segway

When the Segway launched in 2001, the hype was titanic — inventor Dean Kamen called it the most important invention since the Internet, and backers reportedly included Steve Jobs and Jeff Bezos. It was supposed to remake cities the way the automobile had. The engineering genuinely delivered: a self-balancing, gyroscopic machine that worked exactly as promised, smooth and hands-free. And it still missed its promise by a mile, selling modestly for two decades before production stopped.

For founders and operators, this is the canonical case on the gap between an impressive capability and an actual product. The question is never "can we build this?" but who pays, when, in place of what, and why. The case sharpens the discipline of naming the precise moment a customer reaches for your product and the alternative it replaces — and what it means when you can't quite finish that sentence.