I believe we are on the verge of a revolution in economics, and world finance. For hundreds and perhaps thousands of years people have used physical money to represent goods, services and finance. The form of physical money has been trinkets, spices, gems, silver, gold and most recently: paper.
Recently people have become used to the idea that money doesn't have to be a tangible thing. Credit cards have become the dominant means of making financial transactions. Unfortunately credit cards have several serious flaws that cash does not.
Credit/Debit cards take a % of each purchase and charge this percentage toward the merchant selling the goods. So when you buy something the seller has to pay 2-3% of the cost back to the credit card company. Credit/Debit cards are not anonymous, where cash is.
The timing seems right for a new type of currency for the 21st century. Anonymous, electronic money. Imagine if the US treasury issued digital dollar bills. A digital bill would take the form of a small digital file. The file would contain a unique number (lots of 1's and 0's). The file could be saved, emailed, backed-up and traded anonymously.
Such a file could also be copied, duplicated and cloned. To prevent forgery and fraud the holder of a bill could trade the bill for a new bill from the treasury. Such an operation could only be done once for each bill.
If you where doing a financial transaction with a friend you would simply receive the file and save it to your computer. You would trust that your friend wouldn't keep a copy of the bill. If you where doing a financial transaction with someone you didn't trust you would receive the bill, and verify it's authenticity with the treasury department. In return the treasury would issue you a fresh bill in exchange for the bill you received. This would ensure that your bill was unique and had not been copied.
The transactions would be anonymous. The money would be unforgeable. This would be great for world economy as it would make it easy to conduct business without paying the credit card tax or banking fees. Such a system could also be made to prevent money laundering and tax evasion. (The details are too long to explain here)
If the transactions of digital money can be as simple as forwarding files it could be a great compliment to today's green-back.