While it's true that ultimately a company needs a viable business model (e.g. can sell things to customers above cost) it's also true that many of the "unicorns" published by VCs fail to meet this simple criterion and will ultimately cost fools their money. Meanwhile founders can cash out and retire. Additionally, while enterprise products and a few consumer products are easy to validate, no one really "needs" InstaSnap or TweetGram or Facebook or in fact any of the thousands of social media apps that temporarily seem to be winners. So simply talking to potential users is useless because, as Steve Jobs correctly pointed out, "people don't know what they want until you give it to them" - but in fact we can adapt that aphorism to say with even more correctness: "people don't know what they want until they see the people they know using it, and then they will use it too because people are fundamentally herd animals."