Yes, a legit concern! People steal ideas and ideas are priceless!
Really! Not sure! In my life, I did quite the opposite. I always tell as many people as I can, as advanced as possible. I was never worried about people stealing my ideas, rather it's a mistake to keep them to yourself only! Because ideas are always about the execution and they can't steal that.
Some of my best work (from ideas) happened from people knowing what I'm working on and then they offered me some crucial piece of information or help.
So "The most effective thing you can do about your idea is not shut up about what you're doing" ideas are always worth sharing!
Keep spreading your ideas to people! And an idea only to you is No_Idea!
Written by: Mozurul Aziz