The market dropped a lot today, in large part because many think that banks have a lot more exposure left. If banks reported their asset composition better there wouldn't be such a broad based decline.
Bank's are generally excluded from stock selections based on book/market, or cashflow/assets, because empirically these don't work for banks. Hiding information is like crack cocaine, good in the short run, ruinous in the long run. They should realize that greater transparency, more informative information, is better, because right now they trade way below net asset value based on the belief that they could be like UBS or Bear Stearns last year, and have a lot of exposure to a weak asset class that no one knew about. No one knew those companies had $50B in long residential mortgage exposure.
Financial institutions should adopt a more informative reporting policy asap.