Just post I don't know c+++ about supply and demand and you would be better off. Greed has aways been the driving force.
Were Freddie/Fannie not in danger of crashing in 2005, what excuse would Congress have had to open the floodgates to the truly fraudulent lending that's appeared since then? While I won't say greed is never a driving force for Congressional actions, I would consider it a far weaker motivation than CYA.