The now defunct Glass Steagall Act addressed the causes of the Great Depression by separating banks that hold deposits (and therefore should be cautious about our money) from investment firms that make a buck by offering higher profits to investors (by taking more risks). Check out this PBS page for a very good summary of its slow demise. From the final hatchet to the beginning of the end for the country's biggest banks, it took only six years.
It was a simple principle, and it was abandoned slowly over many years, but finally once and for all at the end of 1999. By the summer of 2006, the housing market began to fall, and all those risky investments started to take down our largest banks. Perhaps on the list of places to go from here, we look at places we've been before and remember what we liked about them.