I call this sort of interviewing "Tech Trivial Pursuit"; it's stupid, it won't give you any indication of how the person is going to work out in your team, and it doesn't give any indication of how someone produces a real solution to your actual problems.
It just tells you how quickly someone can come up with a reasonable solution in an interview, and/or how quickly they can remember the solution to your problem that they read in one of the "How to Interview at Google" books.
It's worse when the people interviewing you aren't from the team you'll be working in. I feel bad for those teams... they're going to get someone who's good at answering interview puzzle questions, but maybe they're entirely impossible to work with, or total assholes in day to day situations.
Yeah, yeah, Google's very successful and rich. But it's not because of their broken interview process.