As I write in Subversion Inc., ACORN wasn't solely responsible for the mortgage crisis but it played a significant role in it, pushing the awful Community Reinvestment Act which is essentially a financial affirmative action law. ACORN also intimidated banks into accepting food stamps as income on loan applications.
The radical un-American group ACORN is very much alive despite reports of its demise. It is restructuring in time to help re-elect President Obama in 2012. Obama used to work for ACORN and represented the group in court as its lawyer.