The most successful scam in the Industrial age is the FED's USD since it's survived and endured as long as it has, along with the FED.
Where as the worst scam is extremely likely to end up being the Euro since already it's unraveling shortly after being created and instituted, and causing severe problems for the Euro Union.
Today the smaller countries inside the EU are caught in a maze of unthinkable situations since they don't have the option to simply inflate their way out of their own mistakes concerning their debts with their very own sovereign currencies and electronic printing machines (computers).
So even though the USD can seemingly be thought of by some or even many to be the 'worse' scam, it in fact was and still is the closest to being the most well perfected, evil long con.
Where as it's the Euro that is most likely to unravel first, if any major currency does, not the USD, much to the dismay of the entire European Union.
The EURO is tragically flawed to the point it is extremely likely to be THE BREAKING POINT of the existing International Financial System should it ever completely unravel out of control. (hint) Hope that never happens!
Regardless the EURO itself appears doomed to an early grave no less, and thank goodness since it's severely flawed!
Already many countries in the EURO Union are now presently mired in a severe economic depression that rivals even the so called Great Depression of the 1930s to 1940's. All because their unable to fend for themselves with their own less painful solutions. IE: Their very own printing presses. Of course then the wealthiest would lose out much more than they are now in the Euro Union. Get the point
Okay...here: It's time the Bond holders all take their deserved severe hair cuts. But that wont happen until serious revolts demand it.
What is the "worst scam currency"? That's easy! The EUR.
What currency has done more economic harm to others, than any other currency? The FED's USD.
Who just blew the worlds largest debt bubble in all history, and merely since 2008, at 27 Trillion dollars worth? China.
Who has the worst Debt to GDP ratio in the 1st world? Japan.
Caveat emptor - let the buyer beware!