Bank of America (BAC -0.13%), Citigroup (C -0.32%), and AIG (AIG 0.05%) have all crushed the market over the past year or so, but all three still trade below book value. What causes a stock to trade below book value? In this segment from The Motley Fool's everything-financials show, Where the Money Is, banking analysts David Hanson and Matt Koppenheffer take a question from their mailbag about this issue and tell viewers which of these three stocks they like the best.