I enjoyed, finally, reading Sebastian Mallaby’s The Power Law: Venture Capital and the Art of Disruption this summer. One things that stuck in my mind was Perkins’ Law (named after Kleiner Perkins founder Tom Perkins): “market risk is inversely proportional to technical risk”.
I think that makes a lot of sense. I.e. if the company can build the technically advanced product (and it is likely not be clear that they can), it should be obvious that there is strong customer demand. Otherwise one is probably investing in a technology looking for a problem to solve.