Ask HN: Do you sign NDAs up front?
I've recently been looking for some side iOS work. It seems that everyone wants to protect their idea with an NDA before even talking.
Now if they can make it clear that there actually is some sort of "secret sauce" that's likely to be a truly unique idea, with some reasonable degree of specificity, then sure, I'd consider signing an NDA (depending on the exact wording). To that point, it might be worth having your own NDA drawn up, where you know in advance that the language is reasonable, and proactively offer up your own NDA to these folks, instead of having to wrangle of the language in their NDA.