what about private money?

There's nothing prohibitively problematic about private money; we thrived as a country for a long time without a federal money.

Check out this string of examples from Nicholas Riccardi in the LA Times (by way of LewRockwell.com)...

[In] Pittsboro, N.C....A few dozen local businesses banded together this spring to distribute the Plenty -- a local currency intended to replace the dollar. Now 15,000 Plenties are in circulation here, used everywhere from the organic food co-op to the feed store to, starting this month, the Piggly Wiggly supermarket.

Last popularized during the Great Depression, scrip, or locally created stand-ins for U.S. currency, is making a comeback. Pittsboro, population 2,500, is one of a handful of communities that launched its own money in recent months. It reports an avalanche of calls from other communities that have lost faith in the global financial system....

Over the last two decades, a few communities have created their own cash in an effort to preserve local ties or businesses.

These whimsically named bills -- such as the "BerkShare" or the "Cheer" -- can be spent at neighborhood merchants, who then can use them at other local shops or, should they choose to, trade them in for dollars or other goods.

So far, none of them face the extreme pressures that popularized scrip during the Depression -- bank failures that dried up the supply of cash in circulation, requiring governments to come up with novel ways to keep commerce alive....

In Detroit, for example, the Cheer was created not due to the city's chronic financial woes but because bar owner Jerry Belanger wanted to encourage patrons to support new local businesses....There are now $3,000 worth of Detroit Cheers in circulation after about four months....

The western New York college town of Ithaca is believed to be the first community in recent memory to have revived scrip by starting the Ithaca Hour in 1991. Other places, including followed suit.

Private money is also available in (at least) Mesa, AZ, Portland, ME, and Traverse City, MI.