Though recently under fire, ETF inventor Nate Most says that specialists are critical to ETFs' vaunted liquidity.

The patriarch of U.S. ETFs bemoans the deterrents to global proliferation

Modest-looking but crucial modifications to the fundamental design of Universal Investment Trusts and mutual funds are at the root of SPDRs, WEBS and Diamonds. They have given the American Stock Exchange a new lease on life. The reason is simple: The new structures allow professional investors and money managers to reap important benefits.