No use. I'd rather worry about executing it - and telling lots of people puts me into a place where I "must" execute (or fear someone else doing it, as you said) or let it go.

Works well, saves time.

there is always the risk that someone could take "your" idea.

However, the chances that your idea is unique and particularly special are small. The chances that you'll be able to protect your idea from someone who really wants to steal it are also small.

You are much better served by sharing your idea with a lot of people (might as well make them people you trust, no reason to go out of your way to have someone take your idea), gather as much feedback as possible and build build build.

Your time and effort is much better spent making progress on your idea and moving faster than any idea thiefs than it is worrying about idea theft and trying to protect your idea.

Ideas are generally worthless, everyone has them and on their own don't mean much. Build something of value, then worry about protecting that.