I agree with everything you mentioned in your post, but sometimes its hard to convey an idea on a landing page. A product would be much easier than a service to explain, because you can easily show and describe your product. A service is harder because it takes user action and many times users are skeptical or uninterested in signing up for an idea on a landing page. I think this is where the lean start-up can help speed up the process by figuring out that one dying need you believe consumers want and creating a service solely around that. I think surveys can be most helpful when identifying the strategy to take for a minimum viable product as well.