His most vulnerable answer (in my opinion) was with regard to a question about his most difficult decision so far as President:

The decision to surge our forces in afghanistan. Any time you send our brave men and women into battle, you know that not everyone will come home safely, and that necessarily weighs heavily on you. The decision did help us blunt the taliban’s momentum, and is allowing us to transition to afghan lead - so we will have recovered that surge at the end of this month, and will end the war at the end of 2014. But knowing of the heroes that have fallen is something you never forget.

The session may have lasted only thirty minutes, and he may have only answered ten questions, but the President of the United States’ taking questions over Reddit will be seen by history as a bold and positive statement about the importance of the internet and its native communities.