The most widely discussed and debated unique patient identifier is the patient's Social Security number because it is unique to each individual, unlike the patient's date of birth or the patient's first and last names, which can be shared by multiple people. Although the Unique Physician Identification Number (UPIN) is also a unique identifier, it is used for physicians and not patients. The Social Security number serves as the most effective means to uniquely identify and track patients within the healthcare system.