I'm sure the editorial powers that be at The New York Times, The Guardian, Der Spiegel, El Monde, and El Pais have a very well developed, public-interest-based justification for publishing the WikiLeaks material, but the business people in those institutions have to be happy too. It looks like Cablegate is responsible for a doubling of traffic at The Guardian.
And, as Visual Journalism notes, because the documents are being released gradually, the media outlets that are getting prior access are going to be leading on this story for quite a long time.