If so, they were consistent in disqualifying him in spite of his awesome track record, fame or "street cred" but if not, I can't really justify or defend this type of ceremonial or bureaucratic gotcha interview questions as they are just useless and can be abused by the interviewer to reject applicants they dislike for any reason or whim they might have at that moment.
But my point is this is not a bureaucratic gotcha question. If you can't do this task, you don't really know how to program well. Sorry but that's just how it is. It's like failing FizzBuzz.
There is this culture of crappy software that has happened lately, especially in the Web world, and it is really quite lamentable. I believe that a very large positive impact would be made on the world -- due to the extreme prevalence of software these days -- if more people would take seriously the idea of software creation as a craft with a very high skill ceiling, and work diligently to improve their understanding and their skills.
It is even kind of reasonable to just substitute a call to some black-box is_divisible_by() if you can't figure out how to do that test ...
I, and apparently many others in this thread, spent some time trying to ferret out an answer to what it would mean to invert a binary tree: at first thought it would imply a collection of nodes all pointing at their parents, which seems not very useful (and would require more than 10 lines of code to whiteboard reasonably).
Much of the discussion is about whether or not the problem was described in sufficient detail or not.