Use bitcoins? :-p
Bitcoin is often said to have many of the properties of gold, not least its scarcity.
But here is a clear example of how bitcoin trumps gold, people can move large amounts of bitcoin in a short amount of time with very little risk. Bitcoin users are already doing this.
http://blockexplorer.com/block/0000000000022043f9ea2c298f338...
Total BTC?: 416300.33
At todays bitcoin market value that is 4,605,201.67 USD.
Still some way off 12 billion I grant you, but astonishing considering gold has been used as currency for thousands of years and bitcoin is less than 3 years old.
I'd imagine that governments like the fact that moving their gold is hard, slow, and risky.
This would assume currency value stability over 1000s of years of course, not possible even over decades.