In essence it already is. For every single physical $1 USD bill, you can rest assured there are at least 5 equivalent 'digidollars' somewhere in some high-risk derivative of some sort, or being loaned out in humongous to foreign central banks, or pretty much anything else you can think of other than it actually being loaned out to it's own citizens.
Somebody's debt is somebody else fortune. If you hold e.g. a treasury bill (government's debt) in your hands, you can sell it for cash. All debt, public and private, is about 350% of GDP. GDP is about 16 trln Dollar. Reserves of the banks and currency in circulation is about 1,7 trln Dollars. Now do the math.
