Thing is - if your business will fail because somebody ran off with your idea, you have a problem. Because the moment it looks like you're onto something, somebody will run off with your idea. The only way to keep it secret is to never launch, and that means you don't have a business.
It's more important to be able to move quickly once people copy your idea and stay ahead of them. That means finding a good coder, knowing a lot about the problem domain, and talking to lots of prospects.
Basically, success is all about having many good ideas, one after another. The first one just gets you in the door - it's usually wrong anyways. It can't get you in the door if you never tell anyone though.
The reason for saying that was to outline my fear of luring in a coder by exposing my idea, and having such a person run off with it.