We're perfectly happy eating in a Chinese restaurant. But will we start banking in a Chinese bank?

It's not as crazy as it sounds. As The Wall Street Journal's Lingling Wei reported Wednesday, the Bank of China here in the U.S. has started allowing American customers to open an account and to invest up to $4,000 per day—and a total of $20,000 a year—in Chinese yuan, or renminbi. Until now, you had few options to hold money in yuan, which is a "closed" currency managed, and protected, by Beijing.

The...