Mortgage REITs, like Annaly Capital Management (NYSE:NLY) and American Capital Agency(NASDAQ:AGNC), are trading at deep discounts to their book values, so why aren't these companies buying back more of their own stock?  

In this segment of The Motley Fool's financials-focused show, Where the Money Is, banking analysts Matt Koppenheffer and David Hanson look at two Tweets about the mREIT sector and why buying back shares may not be a complete no-brainer.