Ask HN: Getting a survey of customer interest without giving too much away?

So I've been in the process of developing a new website on the side as something that one day might turn into a legitimate company.

I was thinking that I want to get opinions from my target audience before I get too heavily into it, but I'm a little nervous about giving out too many details about the project for fear that the idea might be "stolen".

While more than likely this is just me being a bit too paranoid, I did want to see what other people had to say about this. How do you go about getting a sense of market interest in a new product and still remain able to protect your idea?

I'm sure the majority of my audience that I would talk to would not have the technical skills nor the desire to rip off the idea, but I can never be sure of course.