Here's an article on Engadget about the AMA: http://www.engadget.com/2015/10/09/stephen-hawking-ai-reddit-ama/
A 5K+ karma AMA on Reddit, and an article on a mainstream gadget website, discussing AI safety and even citing Steve Omohundro, right in the article. This is a huge success. Properly discussed AI risk is now officially mainstream. It makes me proud that I was a part of this success as a SIAI donor.
https://www.reddit.com/r/science/comments/3nyn5i/science_ama_series_stephen_hawking_ama_answers/
the vast majority of the discussion is about AI risk.