It is very very sad day indeed.
He was lucky to have made it as long as he did, he lived 11 months aftetr the doctors gave him 6 to live.. But now he is in a better place.
For all of those who does not know who he is here is a link to his lecture it is one of the best things you will ever watch.
http://www.youtube.com/watch?v=ji5_MqicxSo