There are plenty of good reasons not to sign someone else's NDA, but there's usually a very good reason not to ask someone to sign yours: without the willingnes

There are plenty of good reasons not to sign someone else's NDA, but there's usually a very good reason not to ask someone to sign yours: without the willingness and ability to try to enforce it, your NDA isn't worth the paper it's printed on. In reality only a fraction of the people who enter into agreements actually have the wherewithal to enforce them. This is particularly true when dealing with individuals (especially "entrepreneurs") and small business owners.