When I was working for Opsware, after it had just become a software business, pivoting from Loudcloud, 90%+ of our revenue came from a single, very, very large

When I was working for Opsware, after it had just become a software business, pivoting from Loudcloud, 90%+ of our revenue came from a single, very, very large customer. (And, for the first 6-9 months, they were 100% of our revenue). At every several all hands, I would ask our CEO, "What happens if they decide not to pay us?" - and his answer, at the time, was, "They will pay us" - basically we were betting the company on it - but at least we all knew that. There is a reason why corporations are required to identify if a significant amount of their revenue from a single customer. If you are getting all of your revenue from a single source, the question isn't what to do "if" that revenue disappears, it's what to do when that revenue disappears.