Prosper Taruvinga , Digital Marketing Expert at Livelong Digital Pty Ltd
The dream is for everyone, but the hustle is sold separately. What I mean here is, When you have an idea, it is worth nothing if it's not executed.
So if you share your idea, someone may not execute it as much as you would or as good as you will. You can actually buy lists of ideas ready to implement, so your idea is only as good as the execution.
You wanna know the wealthiest place in the world, Nick? It's not Dubai, It's not America. It's the graveyard!
There you will find, dreams and ideas that were never realised. People die, clutching their ideas, books, or whatever gifts they have because either, they are not willing to execute or share with others what they have.
Usually fear stops people from sharing their ideas. Fear of failure, fear of ridicule. That should not stop you from getting your idea out and getting feedback.
Speaking of which, what was the idea about?
Jef Lippiatt , Owner at Startup Chucktown
building on the previous answer, I would also say that there are really 2 schools of thought.
In the bright world of 2016 most people, companies and definitely Venture Capitalists (VCs) have stopped signing NDAs. Why? It isn't worth their time. Why else? It limits them from hearing an analyzing other ideas in a similar industry or field. It is really only needed if you have and are showing registered Intellectual Property (IP) such as Patents or Trade Secrets.
The argument against NDAs is mentioned above. Execution is key. Everyone has ideas, in fact I have more than 8 notebooks filled front to back with more ideas than I could ever execute on. However in those notebooks they'll never turn into anything. I've tried to give some of the ideas away.
Keep in mind, many people will belittle your ideas. It really is hard to get someone to steal your idea (most people wouldn't want to put in the effort). However, if absolutely no one wants to steal your idea, you may not be trying to create something that anyone (or at least not enough people want or need).
If you aren't sharing your idea, you aren't getting feedback. Chances are, you'll need to make some tweaks to your original idea anyway. So be open about what you are trying to accomplish and realize that there is room for competition and that it is a healthy driver of innovation in and of itself.