That is what Jonathan Gledhill, the Bishop of Lichfield did with his annual message, he posted it to YouTube. Usually the recorded message is shown in all churches in his diocese, but this year as well as that, it was posted online so that it could be shared. He has also gone back and posted the 2005 and 2006 messages.
Of course this is a little gimmicky, but because he is (probably) the first bishop to do this, he garners a little extra reaction in the local press, so that his message is more widely heard, which I suppose is a good thing. But with 53 video views so far, the publicity surrounding the article is probably of greater benefit than the content of the video itself.
Update: It appears that the Archbishop of Canterbury has announced that he will be placing his sermons on youtube as well, in order to make them more widely available (according to the Sunday Telegraph).