But no one yet has unlocked the puzzle of supporting a large newsroom purely on digital revenue, a fact that may presage an era of news organizations that are smaller, weaker and less able to fulfill their traditional function as the nation’s watchdog. “I can’t imagine what civil society would be like,” said Buzz Woolley, a wealthy San Diego businessman who has been a vocal critic of the paper there, The Union-Tribune, and the primary backer of an Internet news site, VoiceofSanDiego.org. “I don’t want to imagine it. A huge amount of information would just never get out.”