In my opinion, this is the question that separates the entrepreneurs from the wantrepreneurs. It's easy to talk the big talk when it comes to startups: how you hire people, how you lead teams, what development methodology you use, etc. When it comes down to it, however, any business is a vehicle for turning money into more money, and your startup is no exception.

Wantrepreneurs think in vague terms about what they would like their company to be. Entrepreneurs think in concrete terms about the money and time commitments it would take to make that happen.

I suggest you randomly pose this question to people: the answers are often very telling.