Commercial Investment Mortgage

I mean I hear about every financial crisis is going on but I do not understand completely. I think some of these investment firms go belly up because of some bad debts resulting from mortgage payments or who were unable to pay their share? I thought that most of these payments mortgage loans commercial or resident's home or business have been taken by banks and non-investment banks? Why commercial banks in the position to buy these companies? How will it benefit?

Please explain if you can.

Thank you!

Hmmm .. nobody answers .. really? Well, I do not know what will happen? All I know is that I thought about it, we only have like 4 banks to choose and we'll start having all these bills! (And I feel like it because I used to have WaMu.)