Regarding NDA's... many (if not most) companies will not sign one, period.
Think about it - there's nothing in it for me, and lots of potential negatives. Let's say you have an idea for an automotive widget and come to me and I sign an NDA. You tell me about your idea and I don't think it's any good. Then, 3 months later you see someone else making it and you assume I told your idea to someone else. Now I potentially have to defend myself just because I gave you time to listen to your idea. Or let's say you tell me and I say "we're already working on something just like that". But you think I'm lying and go to see a lawyer.
Either way, signing an NDA is making a commitment and an agreement, which opens me up to liability. So if I own a multi-million dollar business, why would I risk that just to hear an idea? The answer is - I wouldn't. The only potential upside for me would be if your idea is really great, AND you are willing to sell it to me for a low price, AND I have the time to further/market your idea. Most companies aren't sitting around wishing they had more stuff to do... they are wishing they had more time and more resources to implement the dozens of ideas they already have.
I don't mean to sound down on the inventor... that's how I started, but it's a very hard road to hoe... and the above description is why ideas aren't worth much, and why people usually won't sign an NDA. There's just nothing in it for them. It's the same as me knocking on your door and saying "I have an idea and I want you to be my partner... you supply all the money, time and effort, and I will sit back and collect a chunk of the money"