With a new round of layoffs expected this fall, CBS News is being trimmed to the bone. Rebecca Dana on the dramatic drop in ratings, strange BlackBerry blackouts, and eager suitors for anchor Katie Couric. On Monday, Katie Couric begins her fifth, and quite possibly final, year of hard labor as anchor of the CBS Evening News. However she chooses to mark the occasion, it will no doubt be more subdued than the tears, dancing, and $10 million promotional campaign that attended her debut on Sept. 5, 2006.