These technical interview approaches aren't very good, in my opinion, because they basically assume that the beginning and end of all software development training happened in a second year algorithms class. Algorithms are very cool, I understand why people want to talk about them, but they represent a minority programming challenge in today's world.
Speaking only for myself, in a given month of coding I may only have to consider which algorithms I should use once or twice. The rest of my time is spent on GUI design, communicating with coworkers, working on documentation, and switching between projects. Putting aside the value of algorithms in an interview, how can the interviewer ascertain all of my other software development skills if we spend 2 hours mapping trees on a white board? I would argue that they can't, and by asking technical questions about algorithms or brainteasers, they really aren't properly evaluating the skills of a professional software developer.