I strongly agree with this post. Summary: you have more to gain in idea refinements and reality checks than you have to "loose" from competition. Also NDAs are almost worthless.
That's so true. It's gotten to be such a formality now that plenty of parties don't even bother with them any more. In the US maybe less so that in Europe, but the last NDA I signed is already 2 years ago and it's not like I haven't done anything in that period.
By the time you need that NDA you probably have other problems to attend to.