Whither the broker

Shun Yan Cheung can remember a time when he would have had to pay a broker's hefty fees to invest in the stock market. That's why he invested mainly in no-load mutual funds. But for the last two years, this mathematics professor at Atlanta's Emory University has, along with millions of other Americans, invested on Wall Street from the comfort of his home computer, paying transaction fees that average five dollars per trade, and avoiding brokers like the plague. Using a broker is not even