That said, startups don't need people who like them so much as they need people who trust them. As an investor, customer, or employee, I do need to know that the founder can tell what problems are on the horizon, and is brutally honest about which ones will be challenging. But I also need to know that he'll take care of them, or if not, that he'll hire someone who will (or, if an employee, he'll tell me to do it).
But founders aren't superhuman, and the money involved in successful acquisitions is so high that there are a lot of "companies" working on marginal ideas---ideas that might be big, or they might not, often depending on factors beyond founder knowledge. And at this point I think VC's have to own the responsibility for investing in a high-risk industry.