Of all the interviews I've ever had, this one was the most disappointing. My experience is in NLP, and I specifically applied to Google for a job doing NLP, either in machine translation, speech recognition, or one of the other many NLP tasks they do. My Google interviews were the first ones I had out of college, and I was still naive enough to believe I'd be asked about the stuff I've done and that I'm applying to do. Wrong.
HR apparently just switched my application to a generic new grad job, so the only questions I was asked were generic sorting algorithms and stuff like that. Not a word about machine learning or NLP. Just sorting algorithm basics that I haven't seen since sophomore year and have never and probably will never need to touch in the work place. I've since learned from later interviews and from friends who interviewed at other places: if you're interviewing for anything in software development, there's about a 95% chance you'll only be asked generic technical questions that have nothing to do with the position you're applying for, or the things you'll be working on. It's really sad that even at a top company like Google, this is still the case. I guess you just have to play the system.