Most of it was due to the subprime mortgage bubble. Mortgages were being used as financial securities. It became lucrative to basically invest in mortgages. Mortgages were lent subprime, basically to people who could not afford to own a house. When the bubble burst people were no longer able to afford their homes so many houses were foreclosed on. Many people lost money in investments as well. The panic caused a lot of investors to pull money out of what they could. We are still recovering from the crisis.