Has anyone explored the notion that an employee's abuse of the universal availability rule in a medical flexible spending account (e.g., obtaining maximum reimbursement and then terminating employment) could constitute health care fraud under HIPAA?

I think it probably doesn't fall squarely within HIPAA's fraud, theft & embezzlement provisions but I would be interested if there were any discussions out there...

An FSA is basically employer-provided health insurance (contributions are treated as employer money, and money paid from the account is not included as income), and this is what gives it the tax-favored treatment it enjoys. This is no different than an employee paying $100 into regular group health insurance, getting a $500 treatment, allowing the group health plan to pay for the service, then terminating employment. This is simply the risk the employer assumes, and is not fraud on the employee's side.