The opt-out form requires the user to enter information such as a Government-issued identification card number and Medicare card number. Wouldn't like to think how secure that information will be, after it is submitted and stored!
They do need to validate against the Medicare record, though. So it's kinda needed.
Having said that, I don't believe we should forced to opt out. This whole thing smells like it's for the benefit of big health firms & insurers. Not us.