On the other hand Bitcoin, unlike those other currencies, is not legal tender for paying debts.

WSJ: The Weekend Interview With Gavin Andresen: Bitcoin vs. Ben Bernanke

It is not a governmental instrument of legal tender that requires regulatory legitimacy and coercion by law in order to gain acceptance.

FORBES: Bitcoin Obliterates 'The State Theory Of Money'

But on rare occasions, living people who are not heads of state appear on legal tender.

FORBES: Living People On Legal Tender