It is useful as a gauge of the overall health of the stock markets to keep an eye on how the bank stocks are doing. It is not a large sample, but I keep charts of Citigroup and Bank of America on my screen every day.
In addition to the weakness that has occurred in Citi, probably for the reasons that are widely known, Bank of America (BAC) is looking weaker than usual and there appears to be some distribution.
We are long overdue for a pullback in the broader averages as well as the banks. Particularly when considering that artificially low interest rates seem to have been the impetus for much of this 5 year rally in stocks. There is mixed evidence of the economy improving, but that not withstanding, interest rates will have to be allowed to resume a more market influenced rate sooner or later and that will probably cause a period of volatility.
Otherwise you are an investor.
Know the difference.