Exactly, viable = vendible. If there are no customers, than you didn't make your homework right and built something that nobody wants. I'm affraid that this misassumtion about mobile app can be caused by the feedback from customer interviews. You shouldn't rely too much on what people say, ask them to pay for your product instead.
Lean Startup theory can be pain in the ass for many kind of startups. I think it's wrong that Lean Startup doesn't encourage sales from the very beggining. Sales are the best validation of your idea, not feedback from customers who doesn't pay for your MVP anyways. Build a product for people who pay for it - that's my advice. It's not universal eighter, but more than 50% of startups can start sales before coding anything.
I was only pointing that one special situation, not his whole career. He behaved like a sales genius on that occasion and it doesn't have anything to do with his futher strategy. I wouldn't advise to copy the whole Microsoft strategy.
I think you'd agree that any advice is completely universal. Selling preorders is a solution for most cases, but we of course can discuss the exceptions. If your selling process is different than "get money -> ship the product" than you will always encounter cashflow problems and maybe it isn't so wise to start such a project as a startup.
Yeah, sure - in most cases you can't develop your MVP without money (and in my opinion making it at home with buddies within months doesn't make any sense), but investors are not the only and optimal cash source. It doesn't cost you a lot to start selling your product and get paid by first customers. I started 3 companies like that - I sold the product first and after that started producing it. I think you rather create obstacles and excuses than try to overcome them ;)