My "Housing" dilemma

I do not claim to "know" what caused the current financial crisis. I don't think it is a single person or factor. Lack of regulation is cited to be a major reason. But what I do not understand is what is it that was not regulated enough. Was it the ability of small and large banks/credit unions to lend to people who did not qualify for "prime" loans? Or was it the lack of regulation on how banks and credit services lend to each other and trade with each other? Or was it the lack of regulation on how these subprime loans get lumped together and insured? Greed is cited to be another reason. And any of exactly the same set of people as above (home owner, lender, mortgage firm, mortgage trader) can be attributed with greed as well. Stop here for a minute and think. It is easy to talk about regulation or greed of others. But how far are you ready to blame the single parent with one income for wanting to own a house? Maybe regulation at the bottom level, whereby unnecessarily large loans or loans to "risky" individuals would be avoided like the plague, would have avoided this credit mess altogether. But that wouldn't achieve the original intention: get more people access to housing. I believe Bush came up with the idea of an ownership society. It is easy to lampoon Bush and his half thought through schemes. But at its heart, the idea of enabling ownership of houses/land is a good one. Indian history has shown a remarkable correlation between ownership of land; in this case tied to land reform; and economic and social progress (wish I had a link). Moreover, why is it that Grameen Bank gets a Nobel for issuing what are in effect subprime loans while local banks in the US are being scalped for issuing such loans? Could it be the fact that Grameen's "peer-insurance" as opposed to mortgage insurance in the U.S combined with its reliance on donors is a better model to provide loans to those who cannot afford it?
Or who knows...maybe in fact the problem was caused by huge salaries and McMansions? I would love to find out what percent of the bad loans went to low-income subprime lenders and what percent went towards subprime McMansions.