See the original at XKCD, my all-time favorite webcomic.
Thank you for the insightful and also funny comic. It is true that many twitterers are too focused on their tweets and not the world around them, even though they tweet about the world around them. It is kind of like the people who take pictures of everything, and though they spend so much time taking pictures of beautiful things, they never actually experience the moments they capture.
There is an awesome interview series of social media pros that offers some unique perspectives on topics such as this.