I also asked about whether and how Facebook intended to enforce their platform terms of service, which essentially said apps could use such information temporarily, but that they must discard it no later than 24 hours after a user's most recent use of an application.
I remember that in answering those questions, he essentially said that his preferred approach was not to try and make violations of those terms difficult or impossible through technical means. His inclination was to give apps the benefit of the doubt, and deal with troublemakers if and when issues arise. He also relayed a story about his college days, in which he said that his study of the workings of government was better preparation for his web career than anything directly related to technology.