Government's role in the mortgage industry is up for debate in Congress, and four experts recently engaged in their own debate on the issue. Matthew Richardson, who co-wrote the book "Guaranteed to Fail," blames subsidies for the housing crisis. Real estate and finance professor Susan Wachter says some type of support system must be in place to stabilize housing. Edward Pinto, former executive vice president and chief credit officer at Fannie Mae, says government backing guarantees a failed system. And Terri Ludwig, president and CEO of Enterprise Community Partners, says the government should apply more focus to affordable renting, not just homeownership.