Ask HN: How do you measure fire-in-the-belly?

How do I screen early tech contributors to my startup for their "fire in the belly?" Not everyone is willing to eat Ramen and roll with the punches but the economic climate has made it harder to tell who's really hungry and who's just looking for a meal. We are pursuing a database driven application for mobile. We have some funding but we are running lean and I am afraid of making some bad early hires in this regard. We're in Seattle and I have been initially enthused about some very smart off-the-bench retirees from large local tech companies. I have come to my senses before an offer letter has been written but I am looking for other tips and ideas. See my profile if you would prefer to contact me directly.