That was explained in the audio part of the talk. :-)
Short answer: A long list of attacks in the past have been much harder with large public exponents; using 2^16+1 instead of 3 is a bit slower but is likely to make you safer if someone else gets smart in the future.
Short answer: A long list of attacks in the past have been much harder with large public exponents; using 2^16+1 instead of 3 is a bit slower but is likely to make you safer if someone else gets smart in the future.