what do you think is the main reason for the economic recession all over ?

There are so many reasons for this severe economic crisis. However, I think the main reason behind this is the loss of faith. When even financial institutions lost faith against each other then it is tough to control a crisis. Then it is the inherent tendencies of capitalism to clean itself after some time in the form of bursting of bubbles. This time, since the globalisation is the best at any point of time of the history, the whole world felt the ripple effects of this crisis which started by the bursting of the housing boom.

it is one of the main reasons. there were so many people, who used credit cards for so much they could not return the money. They took home loans where they had no ability to give them back. Not only those people, but why banks gave them loans who can't even afford 1/10 of it?

This recession comes about because of greediness. Everyone wants and the money was spurting around before the downfall. The downfall of the Pyramid schemes also bring about the recession because the money that was put in this scheme cannot be repay back. Greediness is what making the world to be suffering.