They can then spend the electronic currency on multiplayer games, casual games, and virtual worlds.

FORBES: Connect

We already have several very successful methods of electronic currency backed 100% by gold.

FORBES: One Path To A Global Gold Standard

People trying to profit via the bitcoin electronic currency will soon have to work harder to mint the digital coins.

BBC: Rewards set to halve for digital money miners

Instead of bills and coins, we will spend electronic currency -- call it e-money -- that we zap to merchants from our PCs or carry with us on smart cards.

CNN: Cash -- or E-Money?

Liberty Reserve's origins are obscure, but it had grown into one of the criminal underworld's best known electronic currency systems, used by hackers the world over to discreetly move large sums of money across borders, experts say.

WSJ: Costa Rica: Digital currency site founder arrested

Liberty Reserve, which conducted its transactions in dollars, euros and rubles, operates as an anonymous, no-questions-asked alternative to the global banking system, said Aditya Sood, a computer science doctoral candidate at Michigan State University who has studied the electronic currency.

WSJ: Costa Rica: Digital currency site founder arrested

Not that electronic currency is new.

CNN: Cash -- or E-Money?

Currently, transactions within the shadow economy have to be made face to face, but an electronic System D currency would enable remote and even cross-border transactions.

FORBES: Could Bitcoin Become the Currency of System D?

Electronic Arts faced a currency crisis last year when hackers figured out how to make unlimited amounts of "gold" used to buy items on Ultima Online.

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If there becomes reason to question that value, people can switch from dollars to gold currency (most easily through electronic payment systems like debit cards).

FORBES: The Legislative Beginnings Of A Modern Gold Standard