I know a lot of people think people/companies wont steal your idea, however, for me, that is completely context dependent. A big company... well no, I agree. However, a seed funded tech start up, circling in your industry and still searching for a solid business model.....? Too trusting!!
You should be so lucky that someone will steal your idea. The truth is that its all about execution and not ideas. Facebook wasn't the first social network, they just executed better. Same for Instagram, Yammer and Airbnb - all Billion dollar companies built in public.
Ultimately ideas aren't worth a lot, it's honing those ideas into something useful that people are willing to pay for that makes the difference. Plus people tend to be pretty arrogant and have a bunch of (usually terrible) ideas of their own so why would they want to bother with yours? :)
In terms of validating in "stealth" though, if it's a B2C model there are plenty of potential customers out there you can happily share your solution with and have close to zero risk of it spreading any further. You could probably beg them all to tell ten friends each and your secret would still be safe. Trust me, you'll be wondering what you were worried about if you end up proceeding and then have to actually incentivise the distribution of your idea/product!
No one will steal your "idea." Entrepreneurship is 2% great ideas and 98% hard work and execution. You cannot operate your business in fear of others ripping off your success, or you will never find success.
Not to mention, no one will steal your idea until they see it being successful, and at that time you'll already be ahead of the game.
If you have more questions on specifics, don't hesitate to shoot me a message with more specific questions. I'd love to strategize an actionable plan with you to validate your startup.
I have some great experience in this space and I'm confident I could help.
I look forward to your message.
I agree with others that execution, in the end, always trumps just having an idea. That said, I've done a number of alphas and betas and other customer validation tests while trying to keep a product under wraps -- including on behalf of Fortune 100 clients who are extremely concerned about intellectual property challenges. I can certainly help you develop a strategic approach to validating your product with customers while managing the public exposure.