Do your profession a favor and DO NOT sign an NDA in this situation. It's just terrible. Same goes for people that sign non-competes, and thought-police agreements upon being hired.

Don't do it. It's optional, you have the right to refuse. By signing you are putting a huge amount of liability on your shoulders for no reason. You're giving that company the right to sue you for practically any reason they can conjure up.

I don't really see the problem with a simple NDA.

Them: We're going to tell you secret stuff during the interview. Promise not to blab? Me: Yeah, sure.

As far as non-competes and IP-assignment, from what I've seen these have gotten much more reasonable over the past 15 years. If you write or invent it on the job, it's a "work for hire" and the company owns it. What's wrong with that?

If you don't want to sign, that's fine. But there are probably 400 to 1000 other people interested in that open position, and 99% of them are going to sign the NDA.

Them: Please sign this NDA. You: No, I don't sign NDAs. Them (looking at the next guy in line): NEXT!

The company already has the right to sue you for any reason they can conjure up. This is America.

You: "So, what are you guys working on?" Interviewer: "You didn't sign the NDA; I can't tell you."

Yay!