A brief anecdote from Adrianne Jeffries at the Verge about how Social Security numbers, which were not actually intended to be national ID numbers, were misused and confused from the start:

“Social Security numbers were poorly understood from the beginning. In 1938, a leather factory in Lockport, New York attempted to capitalize on the excitement around the country’s newly-formed social insurance program by tucking duplicate Social Security cards into its wallets. Company vice president and treasurer Douglas Patterson thought it would be cute to use the actual Social Security number of his secretary, Hilda Schrader Whitcher.

Real Social Security cards had just begun circulating the year before, so many Americans were confused. Even though the display card was marked ‘specimen’ and sold at Woolworth’s, more than 40,000 people adopted Hilda’s number as their own. According to the Social Security Administration, no fewer than 12 people were still using their Woolworth’s-issued SSN in 1977.”