What’s the best way to know if your idea is a good one?

Seth Godin (Founder at Yoyodyne Entertainment)
Seth’s Blog: Thinking about business models

A business model is the architecture of a business or project. It has four elements: What compelling reason exists for people to give you money? (or votes or donations) How do you acquire what you’re selling for less than it costs to sell it? Shat structural insulation do you have from relentless commoditization and a price war? How will strangers find out about the business and decide to become customers?