Couldn't you say the same for gold?
Say what for gold?
That it's a worldwide currency.
In some aspects, but the fact that it is illiquid and untransferable make it's price much easier to manipulate. You don't buy gold over internet - you buy some guys promise that he has your gold. You can't take 500oz of gold and buy a house over internet, unless you want to give FedEx clerk a heart attack
While with bitcoins, you actually own and spend bitcoins, period. So in that case, worldwide transfer of wealth is simple and instant, nobody can manipulate it's price in any way but selling / buying large quantities of actual coins. Something we don't have with gold, most of which is hidden in a concrete bunker under US desert / WTC / etc, not in your hands. 
