I don’t hire for technical roles, but I always ask a “how would you solve this” question. This gives me an idea about their reasoning and if they have a good grasp of similar situations. It’s not a free consulting session.

Of course, if they ask you about how you implemented the patent protected confabulator at your current role, then there’s a reason to politely decline (and they hopefully wouldn’t hire someone who spills business secrets in an interview).

Depends on the question. "Is this your male member the bird is perching on in the infamous early internet meme?" probably isn't related to any aspect of job performance, at most employers. In which case I'd say yes, you're allowed to refuse to answer.

If the question is job relevant, its more complicated.

You can say “I don’t know that” or “I’d be speculating if I tried to answer that” and then say your approach would be to Google it or whatever the appropriate means of R&D would be.

Wouldn’t they want to hire people who give useful answers to questions related to the company?

I can’t imagine a company that uses interviews as a way to solve problems for free would be in business for very long.

As noted previously: Depends on the question. It is actually illegal to ask some questions, at least in the U.S. Ie. How old are you? Etc.

Cheers, M

You can't possibly give that much value to a single answer to a question that would be considered 'suspiciously useful'.

Sure, if you don't want a job.