That’s what a lot of people wonder at some point, and the answer is: Probably not.
If fact, the problem is that not enough people are copying or stealing your idea.
When other people try to steal your idea is signal that you’re into something great.
Anyway, if your idea is something worth pursuing, sooner or later you’ll have competitors trying to get your piece of the cake.
So, again, is somebody going to steal my idea? Probably not, and it doesn’t matter.
Forget about confidentiality agreements, they’re not going to steal your idea.
(PS. I want to add though, that sharing ideas is a double-edged sword. There are two interesting arguments around this idea that I like. Sometimes they’re opposite but it’s up to you notice the situation you’re dealing with. First, read an article by Derek Siver called Ideas are just a multiplier of execution. But also in the book Zero to One by Peter Thiel, you’ll find that great businesses are built around a secret (idea), so you might want to avoid sharing it publicly. Either way, the main purpose of sharing ideas in their early stage is to get great feedback, and maybe you don’t want to do that with people who are not trustworthy.)