Absolutely the best questions to ask in interviews, in my opinion, are open-ended questions. The problem with those, however, is that the interviewer himself has to know enough to be able to correctly judge whether the candidate's answer is a reasonable one.
Not only that, there are fewer language barriers when asking some canned binary tree bullshit. So a Chinese programmer doing an interview who barely speaks English can still proudly ask the candidate some crap about Heapsort and feel like he's done his job well.
I've had some good luck with open-ended questions like "Tell me about a time when you had to deal with a scaling issue." How they define "scaling issue" often says just as much as their explanation as to how they solved it.
I think I've had to ask for clarification a few times due to the interviewee answering the open-ended question with something I wasn't familiar with, but that's an excellent opportunity to gauge their explanatory skills anyway!
Not only that, there are fewer language barriers when asking some canned binary tree bullshit. So a Chinese programmer doing an interview who barely speaks English can still proudly ask the candidate some crap about Heapsort and feel like he's done his job well.