Why I do not sign non-compete agreements

I agree wholeheartedly.

I do not want to hamstring my future by someone trying to claim (fraudulently or not) that my project is related to some idea that they never did anything with.

In fact, I freely talk about my own ideas with people. If they can execute it better than me, then so be it. There's enough to go around. But, usually, people never take any action, so I'm safe.

Finally, when I talk to other people about their ideas, it's usually not something I'm interested in doing anyway, but I can often help them focus their own ideas. It's good networking!