The article discusses a strategy that may allow an investor to select the single best-performing bank stock each year by buying the one that had he lowest return from the previous year. It is a relative merit type of article. Since 2000, this strategic approach  has produced a roughly 6% better return than simply buying and holding all of the banks. It is a strategy that one might consider if they wanted to invest in this sector and possibly achieve higher returns. It is in no way recommending investing in bank stocks. How is that possibly "another bubble warning sign?"