I’m just throwing out my opinion here. I am a software developer/entrepreneur and this is my thought on the subject:
A) Idea’s are cheap. Implementation is expensive.
B) You’re probably the only one who really cares about your idea.
C) First one up the hill takes the arrows.
Basically: As a developer, I would never sign an NDA just to hear your idea. I have 1,000,000 ideas and so does just about every other person on the planet. You might have a few features that might be useful, but you really just have an idea.
The only benefit you have over anyone else is your passion for your idea. If you start working on your idea/product, you will already be ahead of any “competitors”.
I agree with cwilbur. Google’s idea is “we’re going to build a search engine that doesn’t suck.” If they told me that idea, I would say, “Awesome!” but would not be able to “steal their idea”. Don’t worry about it. If your idea is excellent, you’ll have no trouble getting other people on board to help you out. If it’s not that awesome, they’ll be able to help you out right away.
But if you start asking people to sign an NDA, you’ll instantly cut yourself off from all the best people in the industry. There aren’t many angel investors who will sign an NDA to hear your pitch and the ones that do are probably scamming you. And no developer worth his salt will sign an NDA just to hear an idea. They might have already had a similar idea.
Just start building your product. Be passionate. Be persistent. But whatever you do, don’t get lawyers involved until MUCH later in this process.
Hope this helps.