Even in my limited experience in startups and the film industry, I’ve come to realisation that the best way to pick out someone who doesn’t know what their doing is if they are too paranoid about someone stealing their ideas.
Everything I’ve been taught and have read myself about the film industry is that the studios are extremely conscious about intellectual rights and the danger of being sued. Stories of people being ripped off are actually extremely rare.
The same seems to go for startups. You are never going to get a VC to sign a NDA and you shouldn’t even demand it. They aren’t interested in your idea, they are interested in your execution. Here is an interview with a VC that discusses this topic along with some others.