Liquidity: Liquidity risk for cash alternatives takes two basic forms: lock-ups and liquidity crises.

FORBES: Not All Cash Is Created Equal

"They can use it in an ongoing way to pay bills, save money, get cash and have a real basic, robust, safe and convenient transaction account, " said Treasury Financial Access Innovations Director Joshua Wright.

WSJ: Tax Refunds Move to Debit Cards

There have been some "cash for work" schemes, employing people on basic infrastructure projects like clearing drainage ditches.

BBC: A farmer extracting opium from a poppy blossom