The problem with these questions is the time scale in which they expect the answers. When dealing with a difficult problem, most people don't immediately come up with the right answer and adding in the pressures of an interview only makes it worse. As a development manager, I always ensure that my direct reports know all about the issues they're going to be working on at least one week in advance. I've found that the solutions they come up with are markedly better when they've had a full week of thinking time prior to writing any code.

The alternative interview technique that I like to use when hiring engineers is to send them the questions I'm going to ask a few days before the interview. I ask difficult questions, but there's no surprise. I don't really care if they talk about them with other engineers beforehand...there will always be follow-up questions that I ask to get them to defend their solution that will uncover those that haven't understood the problem fully.