Last year Broadway's 300 customers, many trading from remote locations, accounted for more than 1 billion shares in Nasdaq trading volume0.7% of its total.

FORBES: Free enterprise comes to Wall Street

Frankfurt already leads Europe's other exchanges in several areas of electronic trading, such as remote access.

ECONOMIST: European stock exchanges

While a remote possibility, the SEC has the option of halting trading midday if trading gets overly erratic.

WSJ: Questions Cloud Market Reopening