Marshall McLuhan, famed professor and theorist of media and advertising, said "the medium is the message" in his book Understanding Media. It is also said he predicted the World Wide Web decades before it was invented.
So, it is fitting that we quote McLuhan following the first ever "Twitter Town Hall" and presidential tweet yesterday. The fact that the president answered questions submitted by Tweeters is significant, as he is showing a willingness to communicate via different mechanisms (according to the audience).
I think the next challenge should be answering these questions by Twitter in 140 characters or less. Then I think the medium will influence how the message is received –and professor McLuhan's truism will hold true.