I think that this comes down not so much to the arrogance of "Our idea is so good, we must stop people copying it!", but more the ignorance of "I read a lot about NDAs, they seem like something that might make people take us more seriously as businesspeople".
I believe NDAs make sense when you're developing for unreleased proprietary platforms. If you get outsourcing work to develop a piece of code for the next Samsung phone, preventing you blog the phone spec months before the launch is probably very reasonable. Wannabes adopting bigcorp schemes - it's just cargo cult.
NDAs make sense in a lot of scenarios, just rarely do they make sense right at the beginning of a business relationship.
In my (marketing) work I have never had to sign an NDA to start talking to a company nor have I asked anyone else to do that, however once we move into actually working together then I have both been asked to sign and asked others to, frequently.
Pretty meh. As much as there's a sea of ideas out there, ever increasing is the see of dev and design talent. Get over yourself. If there wasn't such an arrogance around your post I may have given it credence. I can tell you more, but my feedback requires you sign an NDA.