So a hypothetical scenario: a client says to me "I've got this great idea to compete with Facebook by using red navbars instead of blue". Should I refuse the jo

So a hypothetical scenario: a client says to me "I've got this great idea to compete with Facebook by using red navbars instead of blue". Should I refuse the job because their idea won't work? I would clarify what I can and can't do for them: "I can build a working product that will scale to 10,000 concurrent users assuming you're prepared to pay $5K per month in hosting costs. I can't deliver millions of users, protection from patent infringements, etc." Also, if I think the idea is going nowhere, I would be careful about being paid up front. If their happy with my terms, I'm happy to receive their money.