So, I have lots of ideas. You want to share your idea with me, and I sign an NDA prior to hearing it. Turns out I already had that idea, and with that NDA, haven't you basically just stolen my idea from me?

No thanks. I am not a lawyer, I don't trust my ability to parse an NDA and accurately and confidently predict exactly what is covered and what is not, nor do I want to predict whether you tie me up in some bullshit lawsuit that will go nowhere but waste my time and money.

No. I just don't see what is in it for me relative to the risks.