CAMBRIDGE, MASS. — I'm here in the hub of the universe for EmTech, a conference thrown by Technology Review, MIT's magazine of self-importance. Jason Pontin, who is the magazine's editor-in-chief, publisher, and whatever title he's added last week, has just introduced Vinod Khosla, one of the venture-capital industry's brightest names. But is Pontin gazing raptly at Khosla, taking in his every word of wisdom? No, he is not. I can see his laptop screen from six rows away. He is using Twitter, a recent topic of obsession for him. This grand chronicler of innovation is whiling away the duration of Khosla's presentation 140 characters at a time. Oh, wait! I take that back. Now he's reading Valleywag.