SFGate.com, the Chron’s web site, is reporting this afternoon that federal prosecutors have greatly expanded the amount of information they are seeking from the paper’s reporters who investigated the BALCO case. They now want the names of confidential sources for hundreds of articles about the case. “The government’s fishing expedition cannot be countenanced,” attorneys for the Hearst Corp., which owns The Chronicle, declared in papers filed with a federal judge. [PPC yesterday: Reporters avoid prison — for now]