At a news conference, Health and Human Services Secretary Kathleen Sebelius cited half a dozen examples from across the country in which health insurers have sought large premium increases on people who buy coverage individually. In every case but one, state insurance regulators rejected all or part of the requested increases. Ten days ago, Sebelius wrote a letter to one insurer, Anthem Blue Cross of California. She demanded to know why the company had alerted 800,000 policyholders that their premiums would rise by as much as 39%. Anthem postponed the increase by two months.