Gavin Andresen, the 46-year-old lead software developer for the Bitcoin project, is eager to find the answer. “I’m hoping to learn,” he says, whether “a nongovernmental global currency” is possible. “Can you get from where we are to the vision of billions of people all over the world using Bitcoin just like they use any other currency? That’s the grand experiment.”

Thousands of mostly small online merchants are already accepting payment in Bitcoin, though this virtual currency has no intrinsic value and isn’t tied to anything that does. Yet the virtual money that debuted in 2009 with a value of zero and traded for the first time in 2010 at a price of three-tenths of a cent recently changed hands at $97.

For Mr. Andresen, a Princeton graduate who once wrote technical standards for 3-D graphics on the Internet, Bitcoin has already begun to replace the U.S. dollar. In November, the Bitcoin Foundation, where he serves as chief scientist, began paying him in the virtual currency. So far he has persuaded his barber to accept this new money, but only from Mr. Andresen. A haircut costs half a Bitcoin.

The IRS won’t accept Bitcoins, but that doesn’t mean his salary is tax-free. “I get paid in Bitcoin beginning every month. Taxes are computed based on the dollar equivalent.”