They may not be for mainstream portfolios.
Most exchange traded funds grow incrementally as demand grows.
Unlike most exchange traded index products which cover broad markets, these address some of the most volatile sectors of North American equities. Merrill selects the stocks making up the indexes and lists them publicly. The Wall Street Journal has reported hedge funds poaching on the products. Prospectuses for the products offer disclaimers that the products could run up just prior to small investors selecting them, and fall soon thereafter. Merrill is estimated to have pocketed tens of millions of dollars in the run-up of its index products prior to their marketing to retail investors.