I've said it before, I'll say it again, the question is not what backs the money -- gold, silver or nothing -- it's who controls its quantity. Even if you mandate government controlling the quantity of gold-backed money -- as Article 1, Section 8 puts it, "... regulate the Value thereof ...." --
history has shown that once you strap the money supply to gold, the plutocrats will simply manipulate the quantity of gold and thereby have defacto control in no time flat. This has happened time and time again in history.