Many NDAs require the disclosing party to describe, list, or specify the confidential items disclosed. But often I find when very early stage inventors ask people to sign NDAs they often fail to specify what is disclosed even though their agreements require it. If you ever have to enforce an NDA, trying to argue that the entire conversation was confidential is much harder than simply producing the list of disclosures.
Also, I've never asked an investor to sign an NDA. Asking someone to sign an NDA indicates a lack of trust. IMO if you don't trust the people you are talking to you probably shouldn't be talking to them at all.
Recently I've been asked to sign NDAs as part of employment interviews. This seems to have almost become standard practice now. I don't really think this is a great idea, and I often won't take an interview that requires an NDA. But sometimes if I am certain that I won't be developing my own ideas in the field I'll sign one. Inevitably I find that these employment related NDAs are the most frivolous, silly, and irrelevant ones I sign. YMMV.
Recently I've been asked to sign NDAs as part of employment interviews. This seems to have almost become standard practice now. I don't really think this is a great idea, and I often won't take an interview that requires an NDA. But sometimes if I am certain that I won't be developing my own ideas in the field I'll sign one. Inevitably I find that these employment related NDAs are the most frivolous, silly, and irrelevant ones I sign. YMMV.