There are regulations that prevent Social Security numbers from being used for identification. It took a while for my employer to get its administrator, United Healthcare, to change from using the employee's SSN to use a unique employee number. Well, those days are now gone. With Obamacare, health insurance companies will be reporting which people have insurance coverage. And now, since they are part of the tax system, health insurers will now be required to know the SSNs of all of its customers.
This significant expansion of the community of individuals and computer systems that have knowledge of people's SSNs, will significantly increase the opportunity of the theft of such information. So, please beware.