The number of investors using of ETFs, or exchange-traded funds, is surging, and that is music to the ears of WisdomTree Investments (WT 1.33%). In this segment of The Motley Fool's financials-focused show, Where the Money Is, banking analyst David Hanson is joined by Stock Advisor analyst Brendan Mathews to discuss the company massive market opportunity and if a bigger company like BlackRock (BLK) may buy up the smaller player.