> As far as I can see, commercial software isn't limited by "major unknowns" I'm sorry, I needed to get in an afternoon run and actually deleted a paragraph th

> As far as I can see, commercial software isn't limited by "major unknowns" I'm sorry, I needed to get in an afternoon run and actually deleted a paragraph that explained this a little more that I couldn't get just right before posting. I completely agree with you. There aren't a lot of technical unknowns for most things people are trying to do. Thing is, I wasn't actually talking about technical challenges with that point, rather, the requirements that are given at the beginning of a project. The requirements for the new Bay Bridge, for example, are pretty darn clear: make a new bridge from Oakland to Yerba Buena Island. The requirements for making G+ attract Facebook users... errr... uhh... Or how about the requirements for the next Call of Duty to be fun... A great many of today's software projects -- especially those discussed here on HN -- aren't straight up engineering problems, they're more design and UX problems. Even for something like the software for the Joint Strike Fighter, you're more into UX than hard-hittin' avionics for a lot of it these days. And I think that's what makes it hard to predict software development schedules. If we were all building ATM software again and again, we'd be knocking it out of the park. A competitor to Snapchat that is able to sway users over... that might be harder to define up front.