I am an entrepreneur in San Francisco and am afraid to tell people about my business idea without ensuring that I'm legally protected first.
1. They can steal your idea but not the culture of your vision. Worry more on building a team that can sustain your business culture.
2. You can always be dubious, protective and live a life of doubtfulness, or optimistic, indubious, and basically happier,
In both scenarios, you will at times be disappointed by people, and taken advantage of. Better remain a bit naive than all the time skeptical