That is exactly right. To get around PMI and still give 100
% mortgages, lenders were making 80/20 loans. The people who made these loans as well as the people who took them out are largely responsible for this mess. GREED.
You're right about the 80/20 split to get around PMI, but greed is not what got us into this mess. Social engineering, i.e., a Democrat administration and legislature that didn't think it was "fair" that successful people could afford a house, while unsuccessful people couldn't, is what got us into this mess.
Don't blame greed. Greed is liberal-speak for capitalism. The only people who blame greed for America's problems are those who are greedy, but who are not willing to sacrifice and work hard to satisfy their cravings.