Crowd sourced Q&A, AMA all these are really pretty rubbish. It's a celebrity press conference where there can be no follow up questions and the subject can just ignore or brush aside anything that doesn't meet their self-promotion. I'm sure it's an awesome ego boost to the person who is responding, though. For example Norvig works for google. This is not going to press him on goog's and his own ethics with respect privacy, using goog data to deny at risk people insurance, pick your own controversial topic here, in any way but will give him a platform to say "no everything is fine and I and my employer really get this right and nobody should have been worrying in the first place" if he chooses to. Controversial questions will likely be "downvoted" by "fans" as well.
Meanwhile your chances of actually learning anything from this is pretty limited. Norvig likes online courses, oh really? Wow.
Remember the old news model where (at its best) reputable newspapers and magazines would have educated journalists familiar with the topic who would conduct interviews responsibly but in a proper adversarial manner? Wouldn't you prefer something like that with Norvig? Ah well we can dream, huh?