As part of my work and just part of life I talk with a lot of people who are starting companies. Once in awhile people ask me to sign an NDA, I do it but I try to pass on this piece of advice I was given by someone a few years ago:
If you think someone can take the little bit you are going to tell them and pull together a team and execute faster and better than you, than you aren’t the best person to try and build that company, or its not that good of an idea to start with. More often, you are likely to gain a customer or an investor than lose a company or a great idea by not having someone sign an NDA.
Most real VCs and experienced Angels won’t sign an NDA anyway, but I would also apply this to advisors and friends. There are obviously some examples of instances where this wouldn’t apply but don’t assume you HAVE TO have everyone you want to talk to sign something.