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.
I tell everyone my ideas, even as we build them. A perfect example is the question on this site itself: https://clarity.fm/questions/2876/i-am-starting-two-new-companies-but-one-requires-80-of-my-time-how-do-i-hold ...
Someone has started, or "built" and idea, and didn't see it through. Worst-case scenario: you tell someone, they build it, they f*ck up the end-game.
The people that come up with the idea have the passion to see-it-thru during hard-times. People that "steal" your idea, will give up when things get difficult 'cause they don't believe it, they just saw "dollar-signs" and thought it would be easy-money. No such thing as easy-money.