The fact that half of the world's adults don't have a formal bank account is music to the ears of Citigroup (C 0.69%), MasterCard (MA 1.72%), and Visa (V 1.76%). In this segment of The Motley Fool's financials-focused show, Where the Money Is, banking analysts Matt Koppenheffer and David Hanson discuss the incredible opportunity in front of these three companies. Due to their ability to scale operations, David believes MasterCard and Visa are better positioned to thrive in these new markets.