Stan Schroeder from 'franticindustries' explains the digg story life cycle in a post:
Many people think that getting on the front page of Digg is pure luck. You submit a story, then either its noticed and it gets virally dugg to infinity, or no one sees it and it falls down to oblivion. This could not be farther from the truth. Digg is using advanced algorithms and at least a dozen different ways to nurture your story and help it reach the front page - if its worthy. Never will your story be alone, unattended, and unseen: from the first second its submitted and throughout the entire next day, Digg automatically does whatever it can to expose it to people who might find it interesting.
There is a lot of information is this post, even some stuff I never heard or thought about. Quite interesting for diggers, read it here.