An all-out price war officially hit the brokerage industry on Tuesday w/the announcement, first, that Charles Schwab was going to eliminate commissions for certain securities (U.S. stocks, exchange-traded funds, options). Ten hours later, its rival, TD Ameritrade announced that it, too, was going to eliminate commissions. And on Wednesday, E*trade followed suit. Too much pressure from start-ups like Robinhood? A millennial favorite, Robinhood popularized free stock trading years ago.