Blame should go primarily to regulators/ rating agencies and the Governments of affected countries. They just kept their eyes off. They allowed the gambling / speculation to go on and forget the words of Mr Keynes who termed expecting profit to double in one year / one month's time gambling and not expected returns from investment. As I said that blame is to be shared by all stakeholders which includes economists.

Why are we blaming Economists. The blame should go to all stakeholders of the economy. Any one who has little understanding of the economic activities and keep track of those data can feel that some thing was wrong with our economy in 2007. It was too much irrational optimism. Change was taking place but we did not want to notice it- story of frog in a jar. I was really feeling unconfortable with all economic indicators / data for two years culmnating in December 2007.
Yes the causes are too much dependence on Efficient Market theory, mathematical models forgeting the facts that models would generate output based on our assumptions - suiting us and finally credit creation by bank and non-banking industries.
But again our memories are weak so far finance markets go. There were many such financial / economic crises in the past but we forget them fast or don't want to heed them. Therefore in my opinion we will continue to expereince such irrational exuberance from time to tome due to animal spirits we human beings have.