As the popularity of online currency grows, governments should be concerned about losing their monopoly on issuing money. And investors should recognize how much it matters, author and financial journalist Matt Lynn warns.

There is a flurry of new currencies, Lynn writes in a MarketWatch article. Soon to be added to the list are Amazon coins, recently announced by the web's mightiest retailer.

This new currency is designed to allow consumers to purchase items such as apps for Kindle tablets. When the coins launch in May, Amazon plans a giveaway worth tens of millions of dollars. Slate, an online daily magazine, called the coin giveaway “clever monetary stimulus” for Kindle content.