The Google functionality that allows you to search news items by date is a great way to look at the financial crisis that has swept across the world since 2007. If you search for terms like "housing bubble", collapse, CDO or toxic you find articles like this one from May 2004 that talk about the possible toxicity of CDO (collaterised debt obligation, i.e. bundles of mortgage risk, or liquid with very illiquid securities in a collapsing housing market) and their description by others as "weapons of mass financial disruption".

So whilst the some people, notably Warren Buffet saw the dangers, others, such as Alan Greenspan were quick to reassure, saying CDOs "contributed to the development of a far more flexible, efficient and hence resilient financial system than existed just a quarter-century ago”. Even though they were clearly tied to a housing bubble, the existence of which had been known about for some years.

And this piece also talks about earlier warnings such as an Economist article from 2001 called the The Swaps Emperor's New Clothes(pdf).

So, it seems that anyone with any wider financial awareness and nous had, by 2004 and even earlier, a good understanding of the causes of the current financial crisis but that everyone was minting it so heartily, their heads so deep in the trough, that there was no will to stop it.