I was the lead in interviewing several developer hires in recent years.
I remember interviewing for a job myself while I was in a true Dilbert space several years back. I spent more time in Photoshop (because I wanted to and had nothing else challenging to do) rather than in Visual Studio building web applications. If I had plugged-in friends back then, my nickname would have been Wally. So at this one interview I was asked a number of great technical questions about writing applications in Visual Studio and VB. Needless-to-say, I didn't get the job. But I remembered how effective those questions were and how they motivated me to get my act together if I wanted to escape Dilbertville and get back into the game.
When I did re-enter the world of the living and was asked to oversee the interview of prospective developers, I compiled a list of twenty good questions that anyone qualified to write code on my team had to know.
I can say that the questions were definitely helpful, but we all know there's much more to determining the best candidate than basing it on a percentage of accurately answered questions.
I conducted my last interview four years ago. Now I'm sure that interview questions should be both technical and non-technical in nature to determine more about the "person" rather than focus only on his or her developer accumen.
For instance, I think an excellent question would be, "Do you like to drink beer more than eat? Or do you like to eat more than drink beer?"
Any candidate who responds, "Can I get a third option?" would get the job on the spot.