Thomas Peterffy has always been innovative and unorthodox: The 62-year-old, Hungarian-born founder and chairman of electronic options broker Interactive Brokers Group was the first trader to use a handheld computer on the floor of the American Stock Exchange. In the mid-1980s he invested in technology to link stock exchanges globally. Throughout his career he has preached the benefits of access to markets for retail investors.

So when Peterffy sold $1.2 billion Interactive shares to the public last month, he remained true to form: Bypassing Wall Street banks, he hired San Francisco–based WR Hambrecht + Co, a financial services firm that specializes in technology used for offerings, and HSBC to lead a Dutch auction, wherein the initial selling price for shares will always be the highest amount at which all orders can be filled. This format, used by Google in August 2004, gives retail investors an equal shot at buying shares at the offer price, unlike conventional IPOs, in which banks allocate shares to big institutional customers. Peterffy recognizes that the system is a threat to investment banks. “Just as disintermediation in the secondary trading markets leads to lower markups, it is the same for the primary markets,” he says.