Jim McCool, Charles Schwab's executive vice president of institutional business, made waves at an asset-management conference in March when he announced that the brokerage firm soon would offer 401(k) retirement plans stuffed solely with exchange-traded mutual funds - and let investors trade them without charge.

Charles Schwab executive James McCool, shown in 2009, announced the ETF plan in March. 'The idea is disruptive,' one observer said.