[gruez]

>There's no reason for the doctor to involve any patients, other than to write their names down.

...until the patient looks at his health insurance account and notices a charge that he doesn't recognize, or the insurance company decides to do a random audit of a claim.

[SpicyLemonZest]

Right, it's true that insurance companies investigating and denying claims is a major constraint on claims fraud. That's why Medicare and Medicaid still deny a lot of claims (although not so many as UHC) despite being publicly run.