Tell them no, and that you'll be happy to talk to them providing they tell you no confidential information. Their response will give you a good idea of how much they want you.

A good way of reading legal agreements is to assume that someone else will take over (ie it doesn't matter if the person you are talking to now is nice) and what that person could do if they had it in for you. It is extremely likely that the NDA is very one sided. If you really want to wind them up, ask them to pay for you to take the NDA to a lawyer to have it reviewed. After all if the NDA is that important, you should also treat it way.

That said, I know several people who just sign them all without even reading them on the grounds they are unlikely to hold up (one sided) or be enforced.

Generally, requiring an NDA before even talking about the product you would presumably be building; seems like an amateur move. It would make perfect sense for one to be part of your employment agreement though.

If the people you're talking to can't distinguish between talking in general terms about what you would need to be doing to be an effective team member. And talking about the specific details of the product they are building; which they have a right and responsibility to protect. You might want to reconsider working with them.

Eh, I'm leading a project and the owner (non-technical) forced me to have people sign NDA's before I discussed it with them. I personally wouldn't have done it until I gave them actual access to the code. Keep in mind that it could be a completely separate entity than the one you'll actually be working with that enforces the NDA. Most non-technical people think that their ideas are the secrets that need protecting (and the reason they deserve all the money).

Signing an NDA is not really a big deal but the contents of the NDA is what really matters. It is likely that they have lawyer or someone on board who is forcing them to be give undue importance to the NDA.

If they want you to sign a NDA it is your right to read it first. Then I think you can conclude yourself if it is safe to sign or decline to sign.

Another option is to cross out sections you disagree with before signing. It has been a very rare NDA that I've signed that didn't require a lot of crossing out!

Have a lawyer read it to make sure there aren't any clauses that are 'over the top'. A basic NDA should only tell you to not tell anyone the 'secret sauce' and to not talk to press without consent of the company. These aren't things you should really be doing anyways, just now there is a contract reminding you not to.

They've isolated themselves and their product from external feedback before they've even started which is probably a mistake unless they've got major domain expertise.

If you have inhibitions before you've even interviewed then don't work for them.

If you're just curious, decline signing the NDA and see what they say.