This should always freaking be the case. You, the interviewer, are there to decide if you want to work with this person in the future. You're not going to learn that by making an adversary. You're not going to learn that by making it super easy either. If you're worth your salt (as an interviewer, and you should be given that you're now part of the hiring process), you should be able to go through an open ended problem (it's what I do). This open ended problem should have increasingly difficult sub-tasks and of course be related to what you intend the person your interviewing to do. One of my worst experiences interviewing was with a company that clearly didn't give a rats rear end (at one location). Interviewers were constantly late, didn't know what I'd applied for, or even at times my name. Same company, different location...totally different story. Your most valuable resource as a company is your people, treat them as such from start to finish. Needless to say, I chose where I'm at because of the people. I'm glad to see others sharing this attitude as well.