Has the San Francisco Chronicle gone entirely internet mad? For the second day in a row, the limping newspaper has splashed a marginal story about blogging above the fold on its front page, this time a day in the life of Justin Kan, the 24-hour video blogger. The headline blares: It's Justin, Live! All Day, All Night! Appropriate: the newspaper's coverage of internet culture is just as incessant. Yesterday, you'll remember, the anonymous death threats against a little-known online marketing speaker prompted the Chronicle to worry, prominently, that a mob of bloggers was taking the web conversation down into the sewer. Fascinating stuff — unless you're an average reader of the Chronicle, a 55-year-old Daly City insurance salesman approaching retirement, say, in which case you probably want to know more about annuity plans. The Chronicle, fearful of the future of newspapers, may be seeking a younger audience; it had better just hold on to the readers it has. ENLARGE