My own insights: I interviewed for a product manager position. There were hardly any questions about my past/background. most of the questions were about ideas for improvements or additions to google products. The interviewer (who was exceptionally rude and didnt even apolegize of calling 5 hours past the scheduled time) focused on my business thinking (what is the target market, how do you market to your potential clients, what is the business model). How relevant the product is to Google's mission statement seems to be an important part of it.