Quote Originally Posted by angry nomad
Gold and silver cannot be printed.
No, but they are subject to the same forces of supply and demand.

New sources of gold and silver can, and have been found. When this happens their value goes down.

Smart governments do not print more money when they are in financial trouble. Because it is insane.

We do alter the value of our money through a system of altering interest rates that banks can change each other int he short term. This does give us some flexibility in increasing or decreasing the value of our own currency. (And yes, having a weak currency is a good idea sometimes!)

EDIT: The main advantage of having a system where a government can print money at will is that they can expand their economy when needed. Gold, as you mentioned, can't be printed. The US economy has outgrown the gold standard. There simply is not enough gold to cover all its wealth.