Whether some idea is worth something or worth nothing it would be necessary to discloses it to determine that and NDA allows doing that while protecting it. - That is what NDA really does.
Being afraid of nonexistent things is a sign that you are a child. No properly written NDA would ever preclude receiver of information from doing anything that he should be able to do or wanted to do as long as it's in line with business ethics.
Some information that disclosing party thinks is private may in fact be public knowledge, but specific way of implementing it may only be unique to the discloser.
Bottom line: friend or not you have fiduciary legal obligation to protect your company if you have or planning to have anyone else owning any part of your company like employees receiving stock options or there is a chance of selling your company/idea to another entity.
NDAs are enforceable. They have many clauses. Some like reimbursement of loses for unauthorized disclosure of proprietary information is difficult and long to prove. Others, like court injunction from disclosure are fast (1hr - 1day) and don't require any proof if NDA was written properly. But most people, even lawyers, lose sight of second most important function of NDA - it puts other party on notice to treat your information confidential.
If someone doesn't understand what NDA does and that it's a legal requirement you can try to explain to them or just find someone else who will sign NDA, we have 7Bln people.
In addition to NDA
they have to sign IP assignment which is enforceable not only against employees
but also against contractors. You need to know how it needs to be written and
what needs to be done to own all IP developed from your information/resource.
In some cases of significant disclosure you may even need to get Non-Compete signed by a contractor which also puts them on notice not to compete with you. It doesn't preclude them from developing similar functionality for other companies, but it stops them from using information they gained while working on your project to unfairly benefit competing parties. Concept is "you can't un-know" what you know and "Inevitable Disclosure". It's quite easy to succumb to disclosing some once proprietary information if you work for their competitor.