WASHINGTON -- Huge list prices charged by hospitals are drawing increased attention, but a federal law meant to limit what the most financially vulnerable patients can be billed doesn't seem to be making much difference. A provision in President Barack Obama's health care overhaul says most hospitals must charge uninsured patients no more than what people with health insurance are billed. The goal is to protect patients from medical bankruptcy, a problem that will not go away next year when Obama's law expands coverage for millions. Because the Affordable Care Act doesn't cover everyone, many people will remain uninsured. Also, some who could sign up are expected to procrastinate even though the law requires virtually everyone to have health insurance.